Mesozoic granite in South China is an important original rock of ion-adsorption rare earth deposit, while Qidushan granite in Anyuan Country, Nanling, as the bedrock of Shitouping ion-adsorption rare earth deposit in southern Jiangxi, has obvious rare earth mineralization.Methods: In this study, the authors used geochemical and chronological data to explore the genesis and tectonic setting of these granites and their relationship with rare earth mineralization.Results: The results show that Qidushan biotite granite has high content of SiO2, K2O, Al2O3, Fe2O3, low content of CaO, TiO2, MgO, depletion of Eu, Sr, Ba, Ti, P and other elements, obvious negative Eu anomaly, total REE (ΣREE) is 196×10-6 ~ 464×10-6, LREE/HREE is 2.49 ~ 4.39, light REE is slightly enriched, zircon U-Pb age is 143.2 ± 1.8 Ma and 137.1 ± 2.4 Ma, respectively, and they are Mesozoic Early Cretaceous (late Yanshanian) granites with εHf(t) values ranging from-7.6 to-2.6, which belong to fractionated aluminous A-type granites.Conclusions: Comprehensive research shows that it is inferred that granite of Qidushan ,Shitouping, Anyuan Country, southern Jiangxi Province was formed in the extensional tectonic environment, in the crustal source area containing mantle components, which was formed by the subduction of paleopacific plate into the lower crust, plate rotation, crust thinning and asthenosphere upwelling, resulting in the mixing of crust and mantle-derived magma, which melted at high temperature to produce felsic magma, and then rose and emplaced to form Qidushan granite through separation and crystallization. The long-term extension of Mesozoic in southern China is conducive to the formation of highly differentiated granite in Qidushan, and the evolution of late granite to volatile-rich magma-hydrothermal system is of great significance to the formation of heavy rare earth ion adsorption deposits.