Abstract:East Kunlun distributed large areas of intermediate-acid intrusive rocks, providing a natural laboratory for the study of magmatism, and the Late Triassic A-type granites provided new constraints for the tectonic evolution in this area. In this paper, we present a detailed investigation of zircon U-Pb dating, whole rock geochemistry and Hf isotopes of Langmaitan syenogranite in the eastern segment of East Kunlun, in order to identify the chronology and petrogenesis of rocks, and provide a basis data for the evolution of regional tectonics. Syenogranite consists mainly of orthoclase, perthite, plagioclase, quartz, and a small amount of biotite. The zircon U-Pb dating yields an age of 231.5±1.7 Ma, indicating its emplacement in Late Triassic. The syenogranite is geochemically characterized by high SiO2 (72.36%~74.58%) and rich Al2O3 (12.76%~12.89%); relatively rich in K2O (7.52%~7.89%), but poor in Na2O (4.0%~4.25%), low MgO and TiO2; enriched in large ion lithophilic elements Rb, K, etc, depleted high field strength elements such as Ba, Nb, Ta, P, Ti, significantly negative europium anomalies (δEu = 0.04~0.08), these characteristics indicate that they are A-type granites. Mg# is between 0.4 and 0.43, the εHf(t) value is between +2.05 and +7.53, and TDM2 ages between 782 and 1132 Ma, indicating that the syenogranite involvement of mantle components in petrogenesis. Based on the comprehensive regional geology and the characteristics, the Langmaitan A-type granite formed by partial melting of juvenile crust and mixed with mantle-derived materials in post-collision extensional environment.