The Yuqibulake and Wutujinghe plutons in the Boluokenu area are typical mixing granitoids with numerous mafic enclaves in West Tianshan Orogen. Poikilitic, disequilibrium magmatic textures and needlelike apatite are very developed in the mafic enclaves, suggesting an origin of twoend member magma mixing. In contrasting to the host granitoids, the enclaves show relatively lower SiO2, K2O and higher CaO, FeOT, MgO. While, both of the host granitoids and enclaves have a similar characteristics of trace elements with enrichment in LILE, such as Rb, Th, U and K, depletion in Sr, Nb, Ta, P and Ti, presenting a result from the twoend magma mixing. The Yuqibulake granites and mafic enclaves yielded zircon UPb ages of 301 Ma and 308 Ma, respectively. The ages of 303 Ma and 298 Ma were obtained from Wutujinghe granites and enclaves, suggesting that the coeval mantlederived basic magmatism was occurred with this period of granitoid magmatism. The host granitoids have positive εHf(t) varied from +420 to +833 for Yuqibulake pluton and from +497 to +709 for Wutujinghe pluton with TDMC of 782~1045 Ma and 863~998 Ma, respectively, indicating they were partially melted from the early Neoproterozoic crust materials. The enclaves from both plutons also have positive εHf(t) of +275 to +641 and +463 to +792, respectively, similar to those εHf(t) and εNd(t） from coeval basic dykes in western Tianshan Mountais . Combined with the coeval granitoids with higher εHf(t),εNd(t） and medium n(87Sr)/ n(86Sr), we proposed that they were formed by mixing of the magmas from partial melting of early Neoproterozoic crustal materials and from slightly depleted lithospheric mantle. This magmatism evolved from HighK calcalkaline granitoids in Late Carboniferous to Krich granite and Atype granite in Early Permian, representative of products formed in a transitional tectonic setting from postcollision to extension. The crustal extension resulted in mantle upwelling to produce mantlederived basic magma and then trigged partial melting of crustal materials, leading to a strong and wide granitoid magmatism by the mixing of twoend member magmas, and being a significant vertical crust growth in west Tianshan Mountais .