Abstract: Using LA-ICP-MS method, the authors conducted zircon U-Pb isotopic dating of andesite tuffite of Bayan Har Group in the Heishi North Lake area, west Kunlun, Xinjiang.The results show that, after removing the 4 points with obvious U depletion, the weighted ²⁰⁶Pb/²³⁸U age of the remaining 10 measurement points is 252.9±9.1 Ma, which represents the formation time of the magmatic material of andesic tuffite, and the age suggests Late Permian-Early Triassic period.However, the formation of the andesic tuffite was usually later than the eruption, so the volcanic interlayer was formed in the Early Triassic.The discussion on andesic tuffite provides new evidence for the further study of the material composition and formation age of Bayan Har Group in this area.