Abstract: The Paleozoic acidic intrusive rocks are widely developed in the West Junggar and some of them contain dark microgranular enclaves.The study of chronology、geochemistry about magmatic rocks in this area have a great significance for the mechanism of magma mixing and regional tectonic evolution in West Junggar. The Wusan pluton is located in the middle of West Junggar, containing host rock quartz monzonite and micromafic enclaves of quartz biotite monzonite. The concordia age of zircons LA-ICP-MS U-Pb in Quartz monzonites is 280.0±3.8Ma, indicating they should be from in the early Permian. The Rittmann index δ is 3.27~3.36,suggesting that those rocks belong to high potassium calc-alkaline series. Rb, La, Ce, Th, K, P, Zr and Hf are relatively enriched in the rocks, while Ta, Nb, Sr, Ti are relatively depleted, Fractionation between the light and heavy rare earth elements is obvious. In the tectonic setting discrimination diagrams of Y+Nb-Rb and Y-Nb, the data of quartz monzonites plot in the area of intraplate granite, which shows the feature of post-collision granite. The age of the Wusan pluton is obviously later than those of ophiolite, island-arc volcanic rocks and ore porphyry bodies, but synchronous with the A-type granites and bimodal volcanic rocks which were formed in the post-collision environment indicating that the Junggar Ocean may have closed in the Permian. Thus the geochemical and the regional tectonic characteristics indicate that the Wusan pluton may be formed in the post-collision setting. According to the geochemical data and diagrammatize about magnesium in biotite and iron components, we come to the conclusion that the host rock, Quartz monzonite is the I-type granite, the primitive magma of Wusan pluton may come from the crust-mantle mixed source area. Dark microgranular enclaves are widely spread in the Wusan pluton. The host rocks and dark microgranular enclaves have the sharp contact relationship. Most of the enclaves are enclosed in the host rocks and some quartz monzonites are present as inclusions in the dark microgranular enclaves. The crystal of potash feldspar across the host rock and dark microgranular enclaves, and the acicular apatite in the dark microgranular enclaves, shows the petrography evidence of magma mixing. The good linear relationship between the SiO2 content and other oxides of the different minerals in the host rocks and dark microgranular enclaves illustrates they have the some parent magma and were formed by magma mixing.