Abstract: The Datonggou Nanshanbei diorite body is located in the northwest Qaidam basin, with the main rock types quartz diorite, diorite and granodiorite, and it is characterized by high silicon, rich alkali, rich aluminum and poor titanium. A/CNK ranges from 1.52 to 1.57, more than 1.10, and belongs to strong peraluminous granite type. Light rare earth elements (LREE) is enriched while heavy rare earth elements is depleted, and there is negative Eu anomaly. The normalized curve is obviously right inclined, with the feature of enrichment of large ion lithophile elements Rb, Th, K and LREE and the relative depletion of high field strength elements Nb, Ti, Y, Yb. The elements such as Sr, P and Ti show a "V" shaped valley with obvious depletion. The geochemical study shows that the magma is derived from the crust-mantle mixed source mainly composed of arenaceous rocks, and the genetic type belongs to I-type granite. LA-ICP-MS zircon U-Pb dating shows that the zircon formation age is (270±3) Ma (MSWD=0.076), which is the product of magmatic activity in the Middle to Early Permian, and was formed in the island arc granite under subduction environment.