Buddhism first penetrated Tibet when Songtsan Gampo's ancestor Lhato-Thori Nyantsan was at the age of sixty, around the fifth century AD. It was then that a sacred text, a stupa, and a ritual object were said to have descended from heaven onto the roof of the Yumbulakang in Lhoka. But without a writing system the scriptures remained unrevealed, and at first Buddhism spread extremely slowly.

From another angle, the social production of the Tubos took oh a new prosperity from the sixty century. The relationship between the various tribes headed by the Yarlung tribe was consolidated and strengthened, and close political, economic and cultural contacts arose between the Tubos and the Tuguhan and Dangxiang tribes living to the west of the Tang Dynasty and the nations of Nepal and the Pure Land. Buddhism thus entered Tibet mainly because of the needs of the internal social transformation of the Tubos and through the development of external contacts.

In the seventh century, the two brides of Songtsan Gampo, Princess Wencheng of the Tang Dynasty and Princess Bhrikuti Devi of Nepal, each brought an image of Sakyamuni, one from the east and one from the west. It was from this time on that Buddhism actually started to take shape in Tibet, and not long after, the earliest temples such as the Tradrug, the Jokhang and the Ramoche were built in the Land of Snows. During Songtsan Gampo's reign the Tibetan script was created and with the translation of the Buddhist canons, the real spread of Buddhism in Tibet began in earnest. A century later, the thirty-eighth Tubo Tsanpo Trisung Datsan sent special invitations to the Buddhist scholar Shantirakshita and the saint Padmasambhava, built the Samye Monastery at Samye in the Lhoka region, and selected children of wealthy families to enter this first community of monks. He also invited two Buddhist monks from the Han regions to translate Buddhist scriptures and preach Buddhist doctrine, and consequently Buddhism spread far and wide.

At the beginning of the ninth century when the Tubo Tsanpo Tristug Detsan came to the throne, a great number of Indian and Tibetan lotsavas were gathered to translate not only volumes of Buddhist canons but also check the previous translations of scriptures. The amounts of translation were so great that they exceeded the number of volumes translated in the Han regions for over a thousand years. Under Tritsug Detsan's patronage Buddhism prospered, and the king himself set an example of devotion. Parting his hair to the left and right, he tied it with silken bands and then spread it on the floor and asked monks and priests to sit on it as a token of his respect for Buddhism. People gave him the name 'Ralpachen'meaning 'One with long plaint-ed hair.'This Tibetan king established the historically famous monastery of Wushangdo on the southern bank of the middle reaches of the Kyichu River, where he commanded monks to go into meditation and recite scriptures. He also issued a decree commanding every seven households to contribute to the upkeep of one monk, and if anybody committed offences against Buddhists, the Tsanpo punished them severely. How-ever this state of affairs did not last for long. Several former nobles, disgusted with Tritsug Detsan's devotion to Buddhism. Schemed to put an end to his two principal advisers, Tritsug Detsan's elder brother who had become a monk and his tutor, and staged a palace coup by murdering him while he was drunk, The two-century-long period from Songtsan Gampo to Tritsug Detsan when Buddhism was at its zenith is known as the 'Former Prosperity of Buddhism.'Buddhist followers call Tritsug Detsan Gampo and Trisung Detsan the 'Three Ancestral Forefathers.'