The metallogenic belt of Lesser Xingan- Zhangguangcai Range is located in the northeast section of the northern margin of North China Craton, the southeast section of the Central Asian orogenic belt, and the intersection of the outer belt of the Western Pacific Ring, and has undergone multiple phases of superimposed transformations. Its location makes it ideal for the study of tectonic evolution, tectonic domain transition, and tectonism superimposed mineralization in the continental orogenic belt. In this paper, the monzogranite and granodiorite from the Fuanpu molybdenum deposit in the southern part of the metallogenic belt of Lesser Xingan- Zhangguangcai Range are selected for petrology, LA- ICP- MS zircon U- Pb chronology, geochemistry and Sr- Nd- Hf isotope geochemistry studies, and their petrogenesis, magma source zone properties and tectonic background are discussed. The formation age of the Fuanpumonzogranite is 172. 5±0. 8 Ma, and the age of granodiorite formation is 172. 8±1. 1 Ma, both of which belong to the Middle Jurassic. The whole- rock geochemical analysis shows that these granitic rocks are characterized by high 〖JP2〗SiO2 (66. 62%~71. 21%), high K2O (2. 55%~4. 49%), and are metaluminous, showing the characteristics of high potassiumcalcium alkaline rocks. The rocks are relatively enriched in large ion lithophile elements such as Rb, Th, K, U and Ba, and are depletedin high field strength elements such as Nb, Ta, Ti, Yb, Y and P. The fractionation ratio of light and heavy rare earths is obvious and the enrichment of light rare earths ((La/Yb)N=10. 70~34. 04) is consistent with the trace element characteristics of the active continental margin arc magmas. With low ISr. values (0. 7044~0. 7070), positive εNd.(t) values (+1. 77 to +3. 54), young tDM2. ages (671~816 Ma), zircon εHf.(t) values of +6. 1 to +9. 5, and tDM2.=523~699 Ma, the comprehensive study shows that the Fuanpu granitoidswere the result of the depleted mantle material through partial melting to form the new lower crust, remelting to form the acid intrusive rocks. Combined with the regional geological setting, the upwelling of asthenosphere material against the background of subduction tectonics of the Pacific plate to the Eurasian plate and the partial melting of the lower crust may be the mechanism for the formation of this suite of granitoids.