Abstract: The Dongbeigou molybdenum deposit is a newly discovered large-sized cryptoexplosive breccia molybdenum deposit in Kuandian, Liaoning Province. In this study, the authors first carried out a comprehensive study including zircon U-Pb dating, petrogeochemical investigation and Hf isotope analysis of the monzonitic granite related to the Dongbeigou molybdenum deposit. LA-ICP-MS zircon U-Pb chronology indicates that the monzonitic granite was emplaced at (129.4±0.3) Ma. Geochemically, the monzonitic granite has rich silicon (SiO₂=62.21%-83.21%), high potassium (K₂O/Na₂O=3.35-20.27), and rich alkali (K₂O+Na₂O=5.82%-12.23%), belonging to shoshonite series peraluminous granite and characterized by LREE enrichment, HREE depletion, and weak negative Eu anomaly (δEu=0.63-1.07). The monzonitic granite is enriched in LILEs such as K, Rb and Pb, and depleted in HFSEs such as Nb, Ta, P and Ti. According to zircon Hf isotope analyses, the ε_Hf(t) values of monzonitic granite are-12.4——8.5, and two-stage model ages (t_DM2) vary from 442 Ma to 1610 Ma. These characteristics suggest that the primary magma was derived from the remelting of the Mesoproterozoic crustal materials. In combination with metallogenic geological background, the authors hold that the monzonitic granite and the Dongbeigou molybdenum deposit were developed from the subduction of the Pacific Plate beneath Eurasia associated with Cretaceous lithospheric thinning.