Objectives:The Wulanbaixing is located in the western part of the Eastern Kunlun orogenic belt. The study of the Middle Triassic granites in this area not only helps to understand of the Indosinian tectonic—magmatic evolution history of the Eastern Kunlun orogenic belt, but also can provide evidences for the subduction and the closing time of the Paleo- Tethys Ocean.Methods:Detailed geological survey, LA- MC- ICP- MS zircon U- Pb dating of monzogranite, whole rock geochemical and Sr—Nd—Pb isotopes analysis of igneous rocks in Wulanbaixing, Eastern Kunlun orogenic belt.Results: The zircon U- Pb dating of the quartz- diorite and tonalite in southern Wulanbaixing are 235.0±1.0 Ma and 245.4±0.8 Ma, combining field contact relationship it can be ascertained that the granites are the products of Middle Triassic magmatic activities.The whole- rock geochemical analyses show that the Middle Triassic granites in southern Wulanbaixing lie in middle—high K calc- alkaline fields, the Aluminium saturation index show the metalumininous and weak peraluminous features, integrated with enrichments of LREE and LILE（Rb, Th, K et al.）, depletions of Nb, Ta, P and Ti（HFSE）and Eu negative anomaly, high \[n(87Sr)/n(86Sr)\]i(0.709106～0.710136) and negative εNd(t)( -4.18～-5.32), TDM2=1383~1718 Ma, belongs to I- type granites, suggesting plate subduction- related geochemical affinities. Conclusions: Combining achievements of predecessors with this study, it’s believed that the Eastern Kunlun region was in the active continental margin arc environment during plate subduction, and the Paleo- Tethys Ocean was not completely closed in that period.