本文为解决唐代西域史上的一个悬案而作。后西突厥两厢汗国衰亡后，突骑施汗国成为阻止大食东进的屏障，曾与唐朝长期结盟，双方盟与关系的破裂原因一直是个谜。本文认为，双方争战的真正原因并不是贸易纠纷，而在于突骑施苏禄汗国兴起后，迅速包举了西域大量的游牧部族，与唐朝离强合弱、分而制之的意图相悸，其军力之盛，大有成为一个继东西突厥及薛延陀汗国而起的新的北方雄主的气势，已成强藩震主之势，使得一场大战不可避免。突骑施与吐蕃的交通，给了唐廷新的北方孤形包围圈正在形成的巨大震憾，加重了二者攻战的危机。苏禄对唐的几次武力讹诈，加深了双方的猜忌，激化了双方的矛盾。开元二十二年的绢马贸易纠纷保不过提供了战争的口实。 This article is to solve the Tang Dynasty Western Regions history of a pending case. After the fall of the Western Turkestan in the Khanate, the Khanate Khanate became a barrier to stop the Great Eastward expansion. It had long-term alliance with the Tang Dynasty and the reason for the breakdown of both the alliance and the relationship remained a mystery. This article argues that the real cause of the war between the two sides is not a trade dispute. Instead, after the rise of Khuzhu Sulu Khanate, the rapid encasement of a large number of nomadic tribes in the Western Regions is frightening with the intention of the Tang Dynasty to weaken and establish a system of separation and restriction. The rise of its military power has greatly become the momentum of a new northern hero headed by the Turks of Turkistan and of the XUE Yan-Tuo Khanate and has become the dominant force of the fan-clan, making a war inevitable. Kashgar and Tubo traffic facilities, to the new Northern Tang solitary surrounded by envelopes is forming a tremendous shock, increasing the crisis of the two attack. Sulu’s blackmail on Tang’s armed forces deepened the suspicion of both sides and intensified the contradictions between the two sides. The twenty-two years of the horse trade dispute in Kaiyuan provided an excuse for the war.