This paper reports new biostratigraphic data of the Qiangtang area in the northern Tibetan plateau and briefly discusses its significance in marine and continental sedimentary history. The exposed oldest marine strata in this region are the Middle Devonian Chasang Formation. Conodont fossils further confirm a previous conclusion and new outcrops are described. We collected a number of ammonites in the upper part of the Upper Jurassic Suowa Formation in western and central Qiangtang and five ammonites assemblages are established. Especially, the presence of Berriasella sp. and Blanfordiceras sp. indicate that the latest marine strata extend to Tithonian or Berriasian. Scattered orbitolina and special corals are clues that marine Cretaceous maybe exists. The Epigondolella fauna is discovered in the Late Triassic Xiaochaka Formation and is the uppermost conodont zone in Tibet. The ammonite beds were found at the top of the doubtful Shuanghu oil shale section, and all of the fossil specimens belong to Harploceras sp. The age of the oil shale has proved to be early Toarcian and it is related to a global oceanic anoxic event.