Maguan Laojunshan granites located in the Southeastern Yunnan province - Western Guangxi province Sn-W metallogenic belt. To limit the exact age of Late Mesozoic magma-mineralization of Maguan area, samples of the Laojunshan granites have been analyzed by LA-ICP-MS zircon U-Pb techniques, which gives 96±2Ma for the early stage, suggesting an late Cretaceous age. Whole rock geochemistry shows that Laojunshan granites have middle content of SiO2 ( 69.6% ~ 73.6%), high alkali ( K2O + Na2O=6.56%~8.66%), high-K ( K2O > Na2O), peraluminous (A/CNK>1.1) characteristics. Low content of Na2O, CaO and Sr (<50×10-6), high abundances of Rb (>270×10-6), combining with P2O5-Rb and Y-Rb trends indicate that the Laojunshan granites are fractioned S-type granites. Low CaO/Na2O ratios (<0.3), high Rb/Sr and Rb/Ba ratios suggest a plagioclase-poor, clay-rich pelites source. Laojunshan granites and the Late Cretaceous magma-mineralization in Southeastern Yunnan province - Western Guangxi province were formed in the same dynamic background, that was late Cretaceous lithospheric extension in weatern South China. Based on the analysis of regional geochemical anomaly and geological setting, we proposed that the contact zone of the granites (and concealed granites) and the fault system in sedimentary covers are the significant ore prospecting direction in this area.