The Keshuling-Xian'etang greisen-quartz vein type tungsten-tin polymetallic deposit located in Chongyi County of Jiangxi Province is one of the medium-sized tungsten polymetallic deposits in South China. It is closely related to felsic Keshuling granite outcropped in South mining area. SHRIMP zircon U-Pb dating of a fresh granitic sample from the drilling core has yielded ages of 251.5±6.6 Ma and 202±15 Ma. The Keshuling granites fall into the peraluminous, high-K and calc-alkali category revealed by whole rock analysis. SiO₂, total alkaline (Na₂O+K₂O), Fe₂O₃ and FeO contents of the Keshuling granitic intrusion are 73.51%～74.23%, 6.58%～7.77%, 0.01%～0.07% and 0.49%～0.95% respectively. K₂O/Na₂O and A/CNK ratios of the Keshuling granitic intrusion are 1.05～1.98 and 1.17～1.60 (>1.1) respectively. The low REE total content (ΣREE=43.98×10^-6～80.16×10^-6) demonstrates intense differentiation and crystallization at the petrogenic stage, which is the characteristics of typical Nb and Ta-bearing granites in South China. The (La/Yb)_N and δEu of the Keshuling granites are 2.53～7.80 and 0.09～0.20 respectively. According to chondrite-normalized REE patterns, the REE of the Keshuling granitoids have "tetrad effect". Granites and pegmatites of "tetrad effect" are crystallization products of residual melting at the last stage of granitic magmatism. Intensive fractional crystallization can result in enrichment of volatile matters (H₂O, F, Cl, B, P), alkali metals (Na, K) and some ore-forming elements (REE, Nb, Ta, Li, Be) in residual melt. In the primitive mantle-normalized trace element spidergram of the Keshuling granites, defective values of Sr, Eu and Ti show that there existed crystallization and separation of feldspars and ilmenites. The ¹⁷⁶Lu/¹⁷⁷Hf and f_Lu/Hf ratios of zircons in the Keshuling granitic intrusion are 0.000 373～0.003 818 and -0.99～-0.88 respectively, which are lower than those of the upper crust. The ¹⁷⁶Hf/¹⁷⁷Hf ratios (0.281 819～0.282 600), εHf(t) values (between -14.5 and -1.3) and T_DM2 (3.21～2.55 Ga) are representatives of an Archean crustal reservoir. Ca/(Mg+Fe)-Al/(Mg+Fe) diagram indicates that Triassic granitoids in South China mainly originated from metagreywackes and pelites, with the involvement of a small amount of metamorphic basalts and tonalities. Two positive εHf(t) values (+2.4 and +3.0) of zircons indicate that mantle sourced zircons were captured during the elevation and emplacement of felsic magma. Compared with previous achievements, it is suggested that the Triassic granitic rocks including the Keshuling granites in South China were formed in a post-collisional tectonic setting or at the late stage of syn-orogenic tectonic setting. During the relaxation after extruding process, the felsic magmas were fomed by partial melting of thickening crustal materials.