The largest Mesozoic northward transgression in Qangtang Basin of Qinghai-Xizang (Tibet) Plateau occurred during the Buqu Stage, Middle Jurassic. Mainly filled with carbonate rocks, the whole basin is composed of transgression-regression sedimentary cycle. Field outcrops and indoor analysis revealed 8 types of sedimentary facies markers in this region. 4 types of sedimentary facies have been recognized: platform facies, platform marginal facies, foreslope facies and basin facies. Influenced by the northern Lazhuglung-Jinshajiang suture zone, central uplift region and southern Bangongco-Nujiang suture zone, these facies belts extended east-west. The sedimentary model was established based on observed depositional features. From their biological features and sedimentary characteristics, it is suggested that the paleoclimate was warm and humid at that time. The Buqu Formation is a promising target for oil and gas exploration in Shuanghu-Duoyong area in future. The largest Mesozoic northward transgression in Qangtang Basin of Qinghai-Xizang (Tibet) Plateau occurred during the Buqu Stage, Middle Jurassic. Mainly filled with carbonate rocks, the whole basin is composed of transgression-regression sedimentary cycle. Field outcrops and indoor analysis revealed 8 Types of sedimentary facies markers in this region. 4 types of sedimentary facies have been recognized: platform facies, platform marginal facies, foreslope facies and basin facies. Influenced by the northern Lazhuglung-Jinshajiang suture zone, central uplift region and southern Bangongco-Nujiang suture zone, these facies bels extended on east-west. The sedimentary model was established based on observed depositional features. it is suggested that the paleoclimate was warm and humid at that time. The Buqu Formation is a promising target for oil and gas exploration in Shuanghu-Duoyong area in future.