The Mesozoic magmatic activity in the Bozhushan area of southeastern Yunnan plays an important role in regional tectonic evolution and mineralization. A large number of aplite bodies are developed around the Bozhushan pluton in this area, yet previous studies on the timing and petrogenesis of such rocks remain limited. This paper focuses on the Dashanjiao aplite in Bozhushan and investigates its genesis and metallogenic implications through LA-ICP-MS zircon U-Pb dating, whole rock major and trace element analysis, and zircon Lu-Hf isotopic testing. Dating results indicate that it formed in the Late Cretaceous (89.1~87.5 Ma), consistent with the age of regional Yanshanian granites. Geochemical characteristics reveal that it is a highly fractionated S type granite, characterized by peraluminous to metaluminous composition, enrichment in silicon and alkali, and depletion in magnesium and iron. Zircon εHf(t) values range from -7.79 to -5.07, with t_DM2 model ages of 1 451~1 300 Ma, suggesting that the magma was derived from partial melting of Mesoproterozoic crust. The pluton formed in a post collisional extensional setting under the background of Pacific Plate subduction. Its geochemical features (e.g., depletion in Ba and Sr, high Rb/Sr ratio) reveal significant magmatic crystallization differentiation. Combined with previous research findings, it is concluded that the aplite and the granites in the region are products derived from the same source region but underwent different degrees of crystallization differentiation, the Late Cretaceous highly fractionated S-type aplite originated from the low-temperature melting of Mesoproterozoic clay-rich crust, and the associated magmatic hydrothermal differentiation process played an important controlling role in regional W-Sn-Ag polymetallic mineralization.