Abstract: The Xinjing quartz-diorite, lies in the Beishan area, Gansu Province, is occurred in the Paleozoic Beishan island arc belt. The results of petrochemistry show that, the contents of SiO₂, Al₂O₃ and MgO are (59.13%~67.90%), (14.90%~16.42%) and (1.96%~3.12%), respectively, while the values of trace elements (such as Y, Yb and Sr) are (11×10^-6~22.8×10^-6), (1.19×10^-6~2.33×10^-6) and (364×10^-6~871×10^-6), and these rocks show positive Eu anomalies, indicating that the plagiogranite porphyry shows characteristics of adakitic rocks.These adakitic rocks were formed by the partial melting of subducting slab with MORB features under some physical and chemical conditions, and then they were directly emplaced to the near surface. Thus, these adakitic rocks have close spatial temporal relationship with gold mineralization in this studying area.