The large- scale gold mineralization in the Jiaodong area is closely related to the Mesozoic Guojialing magmatic activity, but the origin of the Guojialing magma is still controversial. This paper, the Guojialing Congjia pluton, which has a time—space relationship with the gold deposit in the northern part of the Jiaojia gold belt, isselected as the research object. Petrography, geochemistry, LA- MC- ICP- MS zircon U- Pb chronology and Sr—Nd isotope studies are carried out. The Na2O/K2O values of Congjia granite are 0.69～1.23, the Na2O+K2O values 7.29%～9.58%, and the A/CNK values 1.39～1.51, which are peraluminous granites of high potassium calc alkaline series. Congjia pluton is characterized by enrichment of LREE, depletion of HREE, negative Eu anomaly (0.41~0.68), enrichment of LILE such as Ba and Sr, depletion of HFSE such as Nb, Ta and Ti, and high Sr/Y ratio (81.59~235.48). The zircon U- Pb age is 126.07±0.3Ma, which can represent the crystallization age of Congjia pluton. The 87Sr/86Sr value is 0.711463, indicating the participation of mantle derived materials. \[n(87Sr)/n(86Sr)\]i is 0.711117, Nd (t)is -17.14, TDM2 is 3396Ma. Based on analysis, the granite is formed by the mixing of mantle derived basic magma and acidic magma during the remelting of the lower crust. The magma is assimilated and contaminated by Linglong granite during the upwelling process. It is a typical granite formed by the direct participation of mantle derived materials in the mixing of crust and mantle.