Usually associated with large-scale tectono-magmatic activities, granitoids are widely spread in Beishan area. This paper mainly focuses on the geochronology of the granite in Mingshui area. Based on the40Ar-39Ar isotopic dating of biotite from the granite in Mingshui, the authors obtained a plateau age of 218.4±0.5 Ma, which indicates that the granite in Mingshui must have intruded during the Indosinian movement and might have been produced by eventual collision between the Tarim and the Kazakhstan plates.