Bayinbuluke pluton is one typical representative of granitic intrusions exposed in the northern margin of South Tianshan and composed mainly of monzogranite and K-feldspar granites. Both rocks are characterized by enrichment in Rb, Ba, Th, K and Sr, poor HFSE and depletion of Nb, Ta, Ti and P, geochemically similar to those of island magmatism occurred in active margins. Of them, monzogranite has relative low SiO2 and K2O, higher CaO, Fe2O3T and MgO, showing LREE-enriched and HREE depleted REE patterns with slightly negative Eu anomalies. Whereas K-feldspar granite has higher SiO2 and K2O, lower CaO and MgO contents and strongly depleted in Sr, Ba, Eu, Ti and P, displaying medium LREE-enriched and HREE-depleted REE patterns with strong negative Eu anomalies. Furthermore, both of them have higher DI (94.31~95.52) and Rb/Sr ratios. All suggests that it likely resulted from the higher differentiation of calcalkaline magmas. Zircon U-Pb dating yields forming ages of 452.2±5.3 Ma and 4302±3.2 Ma for monzogranite and K-feldspar granites, with the εHf(t) values ranging from -8.89 to -6.80 and from-5.33 to-2.19 as well as TDMC of 1.58~1.69 Ga and 1.33~1.49 Ga, respectively, suggesting they were derived from MesoProterozoic crustal materials in the basement. Combined with coeval granitoids occurring widely in both South Tianshan and southern margin of central Tianshan, monzogranites and K-feldspar granites are reprehensive of arc magmatism during early subduction and later mature arc period, suggesting that subduction of South Tianshan ocean crust continued till Silurian.