Many Tibetan history books record that it was from the reign of the 27th king Lha Thotori Nyantsen (around the year 333) Buddhism was formally introduced into the Tubo Kingdom. But only some sutras, small pagodas and other Buddhist objects spread to Tubo then. Buddhist activities such as copying, translating, chanting and preaching sutras, had not yet appeared in Tubo. Hence, one cannot deem it as the Official introduction of Buddhism into Tubo.

The statues of Songtsen Gampo, Princess Tritsun and Princess Wencheng enshrined in the Trandruk Temple in Shannan prefecture, Tibet.

In fact, it was from the reign of Songtsen Gampo that Buddhism began to really spread to Tubo. In the 7th century, the Tubo Kingdom experienced unprecedented development, in particular after the King Songtsen Gampo. After Songtsen Gampo succeeded to the throne, Tubo adopted a series of open policies to introduce advanced science, technology and cultural knowledge from its neighboring countries and regions. Tibetan historical records show that Songtsen Grornpo created characters for Tubo. Tonmi Sambhota, a famous civil official during the reign of Songtsen Gampo, used to imitate an ancient Indian script to invent Tibetan writing. Many Tibetan historical records have detailed descriptions on this. The creation of Tibetan writing was smooth and rapid and the script was soon put into practical use. In particular, Songtsen Gampo himself by taking the lead in learning the newly created written language, became the first Tsenpo proficient in it and set an example for the application and popularization of the language. The invention of Tibetan written language created the right conditions forthe introduction of advanced culture, science and technology, marking the beginning of a new civilization. In the middle of 7th century, Tubo had the ability and the right conditions to translate sutras, laying a foundation for the official introduction of Buddhism into Tubo.

The 21 sutras and tantras of Avalokited vara exalt the virtues and feats of Avalokitesvara, helping disseminate Buddhism in Tubo through prophecy or impartation. From then on, Avalokiteg vara has been deemed as a Bodhisattva who liberates all sentient beings of Tubo from worldly sufferings and the Red Hill in Lhasa emerged as the religious site of Avalokites-vara, called Potala. Later on, Lhasa gradually became a sacred Buddhist place.