Abstract: The post-collisional tectonic-magmatic activity in Xinjiang region is very intensive, and the isotopic age of the activity ranges mainly from 270 to 290Ma. The study on post-collisional tectonic-magmatic activity is limited and relatively weak in this region, due to the lacking of high quality chronological data. On the basis of field geological investigations, we analyze the Xiaopu granite mass of Harlik region in the eastern Tianshan. Zircons from these plutons are dated by LA-ICP-MS U-Pb method and yield weighted mean age of 297±2Ma and 295±2Ma respectively, which is considered representing early period of post-collisional magmatism. The Xiaopu granite mass mainly consists of plagioclase,quartz,K-feldspar,amphibole,biotite,and some accessory minerals such as zircon,apatite and magnetite,with a similar mineral assemblage with the typical I-type high-K calc-alkaline granite. The triplet of basic dyke swarms, kaligranites as well as alkaline granites could be regarded as a prominent indication of the initial stage of post-collision, and they occurred synchronously and coexisted in Harlik region. According to the regional geological data, we concluded that the Early Permian Xiaopu granite mass was formed by partial melting of lower crustal materials under the thickening crust during the early post-collisional extension, and the tectonic affinity of the granite mass belongs to intraplate magmatism.