西藏民族從唐朝時期一躍成為東亞的強大勢力，後來隨著唐朝滅亡，吐蕃也跟著分裂與崩壞。本文主要探究唐代吐蕃興衰原因，以宗教觀點，研究其對政局的影響。在吐蕃亡國眾多因素中，本文特別聚焦在政教關係上。筆者將唐代吐蕃分為兩期，前半期的興盛，後半期開始漸漸走向滅亡。吐蕃王朝自始自終朝廷內皆有兩敵對集團互相鬥爭的狀況，然而兩集團敵對不見得就會使國家處在內鬥或失去向外擴張的機會。墀松德贊贊普以前，即便權臣控制王室，也以擴張領土為優先政策。但其以後的吐蕃卻在推廣佛教下，宮廷內鬥更趨嚴重，國家經濟財政也往不平衡的方向前進。墀德松贊贊普開始，為了將王室長久的敵人本教勢力給徹底解決，大力推廣佛教，僧侶甚至能坐上百官之首的位子。這就是為何在吐蕃宗教會牽扯到政局與形成特殊相制的原因，此為整個西藏歷史特殊之處。佛教勢力地位提升，也標示著本教勢力官員們的地位將大幅降低，為顧及自身生存之空間，不得不對王室大反撲，墀祖德贊贊普最終被暗殺身亡。繼任者朗達瑪可能為了緩和衝突氣氛，便開始修正興佛政策，但國家內部總總矛盾勢必將吐蕃帶向滅亡。朗達瑪無力可回天，便被後代佛教史觀之教法史料視為代罪羔羊。
Tibet people from 7-8th became the powerful empire in East Asia. When Tang Dynasty demise, Tibetan also had split along with Tang dynasty. This paper is focus on the reason for the rise and fall of Tibetan. Including religious, Evolution of the monarch and the prime minister. Tibetan in Tang dynasty in my research can look like two parts. The first half situation is rise. Another one is gradually to start die out. Tibetan always had two groups that they are rival and fight each other. This situation made country lose opportunity to development, but on the other hand it can help Tibetan to expand outward. Before the monarch Khri srong lde btsan, Tibetan was striking terror in Asia. It has even captured the capital of the Tang Dynasty. After this time country became to stage of weakens. It can take the blame for the Buddhism. When the monarch Khri lde srong btsan, in order to confront with another part. He used to promote Buddhism and enhance the welfare of the monks. In this time, even the monks can do the prime minister. The Conservative Party was dissatisfied with this policy. They killed the monarch Khri gtsug lde brtsan. Next successor had some policies which can restore normal political situation. But it has been unable to return XXX. Finally, the Tibet eventually collapsed in AD 905 years. Tibet existed about three hundred years in the history.
