The LA-ICP-MS U-Pb dating and petrogeochemical and Hf isotopic analysis were carried out in this study to understand petrogenesis of maficultramafic composite pluton in Niubizishan and subduction effect of South Qilianshan on the Tarim basin. LAICPMS UPb dating of zircon from diorite body shows that the diorite formed at Late Devonian (361±3 Ma, MSWD=0049). Petrogeochemical analysis suggests that the diorite has SiO2 content of 5344%~5827%, Na2O+K2O of 480%~639%, and K2O/Na2O ratio of 033~097, indicating the rock is enriched in Na and falls into the calcalkaline to highK calcalkaline series. Primitive mantlenormalized trace element spider diagrams show relative enrichment of LILE (such as Rb and K) and LREE, relatively depletion of HFSE (Ta, Nb and Zr), Th=203×10-6~657×10-6, Th/Ta=273~ 1282, all of which suggest they were the product of crustmantle mixed magma. In addition, discovery of gabbro enclave in diorite also shows mixing of crustal and mantle magma. The Hf isotopic also shows that εHf(t) values of the diorite vary from ±641 to ±936, and twostage model ages (TDM2) vary from 714 to 878Ma. These characteristics suggest that the primary magma was derived from the depleted sources and remelting of Neoproterozoic juvenile crustal materials. Based on previous and present study of structural setting, it can be concluded that the diorite from the Niubiziliang intrusion formed in an extensional structure setting, which could be related to the subduction of the South Qilian Orogenic belt beneath the Qaidam block.