Abstract: Qiangtang basin locates in the north and mid potion of Qinghai-Tibet plateau,where widespread Mesozoic marine deposits. Mesozoic Qiangtang basin has high quality hydrocarbon source rocks. The thickness of source rocks is huge. The organic matter type of source rocks is perfect and its abundance is large. In the upper Triassic Xiaochaka Formation and the mid Jurrasic Buqu Formation and Xiali Formation the organic matter maturity varieties from mature to overmature. The burial conditions of source rocks is a relative perfect,and oil production is excitement large. The Mesozoic source rocks are one origin of oil and gas in Qiangtang basin. The characteristic of reservoir and cap rock is very superiority in Qiangtang basin. It is confirned that there are three petroleum systems of J3s、J2b and T3x in Qingtang basin by Magoon's petroleum system, and there are two key stages in Qiangtangbasin:later Jurassic-early Cretaceous and later Tertiary. The collocation of space-time is very nice.