Abstract：The formation age of Jiaoyuqiao Group, i.e., the metamorphic rocks in the northern margin of Gangdise, is still in controversy. High resolution LA-ICP-MS in situ U-Pb analysis was conducted for the intercalation of garnet-bearing green schist in marbles of upper Jiayuqiao Group at Bajian Village, Baxoi County, Tibet, and an upper intercept age of 566±27 Ma was obtained. This result cinfines the formation age of the Jiaoyuqiao Group to late Sinian. Combined with related data, the authors hold that there existed a large continental margin rift in the northern margin of Gangdise in late Sinian-Cambrian period.