The most significant innovations carried along the Silk Road to China were the belief systems and religious arts of India, Central Asia and the Middle East. Buddhism began its evolution as a religious doctrine in the sixth century BC, and was adopted as India's official religion in the third century BC. When Buddhism, and to a lesser extent Manicheanism and Nestorianism arrived in China, their art and creed revolutionized Chinese culture. Many of the structures housing ancient religious manuscripts, beautiful frescoes and statuary - built from the first century BC to the end of the Tang Dynasty - lay hidden under centuries of sand until their rediscovery at the turn of this century.

According to legend, the Han Emperor Mingti, who had already heard of Buddhism, dreamt of a golden figure floating in a halo of light - perhaps a flying apsara (Buddhist angel) - that was interpreted by the Emperor's wise men to be the Buddha himself. Consequently, an envoy was sent to India to learn about the new religion, returning with sacred Buddhist texts and paintings as well as Indian preists to explain the teachings of the Buddha to the Emperor. Monks, missionaries and pilgrims began travelling from India to Central Asia and then on to China, bringing Buddhist writings and paintings, while converts followed the Silk Road west. The new Buddhist art that emerged from Chinese Turkestan, now known as Serindian, absorbed different styles and forms along the way, including those popular in the Kingdom of Gandhara (in what is now the Peshawar valley of northwest Pakistan), where indigenous Indian art forms had already been mixed with those of the Greeks and Persians in the early sixth century BC.

This Graeco-Indian, or Gandharan art was considered revolutionary for its depiction of the Buddha in human form, the temporal earthbound personality of Sakyamuni. Since Sakyamuni had achieved nirvana, escaping the cycles of birth and rebirth, he had essentially ceased to exist. He had previously been symbolized by a footprint, a wheel, a tree, a stupa or Sanskrit characters. The Greek (Hellenistic) influence on traditional Buddhist painting was obvious: instead of a loincloth the Buddha wore flowing robes, had a straight chiselled nose and brow, full lips and wavy hair. Some of the Indian influences that remained were the heavy eyelids and elongated ear lobes, stretched long because of Sakyamuni's former life as a heavily jewelled and worldly prince, a symbol of the life he renounced for the ascetic spiritual life. As a result of rushed and highly unprofessional excavations in the cities and temples of Gandhara (which were already in extremely poor condition), most of the wall paintings and frescoes were destroyed and sculptures are all that remain of this exquisite art form. Nonetheless, it was this art form that travelled across the Pamirs, establishing itself in the oasis towns of the Taklamakan and beyond, where it was again to absorb new influences.

With the rapid spread of Buddhism along the Silk Road, elaborate cave complexes and monasteries were built in and around the oasis towns, generously supported by powerful local families and merchants to ensure the safe passage of their caravans. Many of the cave frescoes portray these benefactors in pious positions, sometimes by name, since these gifts were believed to help them in their quest for nirvana. Pilgrims from China continued to travel west searching for original manuscripts and holy sites, over the Karakoram range to Gandhara and India.

The first Chinese pilgrim to actually reach India and return with a knowledge of Buddhism was Fa Xi'an (337-422), a monk who travelled the southern route in 399, through Dunhuang and Khotan and over the Himalayas to India. He studied Buddhism under various Indian masters in Benares, Gandhara and Ceylon (Sri Lanka), and went as far as Sumatra and Java in Indonesia; altogether he visited over 30 countries, returning to China in 414 via the sea route. The Buddhist monk, Xuan Zang (600-664), is perhaps the most well-known of all Chinese travellers on the Silk Road, and one of the four great translators of Buddhist texts. His lasting fame is primarily due to the humorous 16th-century novel, Pilgrimage to the West (also known as Monkey), a fictional account of his pilgrimage that includes and odd assortment of the characters who accompany the monk on his journey, along with their various escapades.

Xuan Zang left Chang'an in 629 and travelled along the northern Silk Road to Turpan, Kucha, then onto Tashkent, Samarkand and Bactria, over the Hindu Kush to Gandhara and eventually further south to Sri Lanka. He studied Mahayana Buddhism, particularly the Yogachara school, at various monasteries for 14 years and became a renowned scholar, winning many debates against Hinayana Buddhist scholars. He returned to China in 645 via the southern Silk Road and wrote Records of the Western Regions, an excellent account of his travels and the state of Buddhism in the seventh century. With a disciple he co-founded the Fa Xiang school, the Chinese form of Yogachara, which was popular during the Tang Dynasty. The central tenet in this belief if that the external world is a product of our consciousness, things exist only as far as they exist in our minds, and nirvana (Buddhahood) is achieved after working through several complex levels of spiritual development and detachment. The Fa Xiang school denies that Buddhahood is possible for everyone, in direct opposition to other Mahayana schools, and it actually contributed to the latter's decline after the Tang Dynasty. Xuan Zang translated over 75 Sanskrit works into Chinese, and translated the teachings of the Taoist philosopher, Laozi, into Sanskrit as well. His translations were known for their high literary content and he was instrumental in creating an extensive Buddhist vocabulary in Chinese. The Big Goose Pagoda in Xi'an was built to house the 520 Mahayana and Hinayana texts and various relics that he brought back, and this was where he worked for the remainder of his life, translating sutras.

The religions of Manicheanism and Nestorianism were also introduced, accepted and assimilated along the Silk Road, although neither reached the popularity enjoyed by Buddhism. Manicheanism was started by Manes of Persia in the third century BC and is a religion based on the opposing principles of light and dark (spirit and flesh). Followers of Manicheanism, persecuted by the Christians in the fifth century AD, began arriving in Central Asia and flourished during the Sui (581-618) and Tang dynasties. Until the recent discovery of Manichean Libraries and wall paintings at Kharakhoja (near Turpan), little was known of this religious sect, believed by most scholars to have no literature or art. It sustained a substantial following into the tenth century, but then quickly disappeared with the advent of Islam in the West and Buddhism in the East.

One of the essential beliefs of Nestorian Christianity was that Christ could not be disciples fled east to the Sassanian Empire (present-day Iran), and then to China in the seventh century. Nestorian manuscripts were discovered in the Turpan and Dunhuang regions, and Marco Polo found traces of the religion in Kashgar and Khotan as late as the 13th century, even though all foreign religions were officially banned by the Chinese in 845 and virtually wiped out by the Islamic crusades in the 11th century.