Yunxian granite in South Lancangjiang convergent margin comprises mainly diorite monzonite granite and belongs to the potassium_rich calc_alkali series, with SiO2 being 68。57% and K2O/Na2O 1。67 on average. The acidity and alkalinity of the rock are lower than the average values of the same kind of rocks, and its mafic ingredient is higher than the average value, suggesting that the rock is somewhat intermediate and similar to the syn_collision type granite. Yunxian granite is peraluminous, with Al2O3 being 13。66% and A/CNK 1.1 onaverage and the corundum molecule more than 1% according to CIPW. The rocksare on the whole relatively rich in LILE but poor in HFSE and shows moderate negative Eu anomalies with δEu being 0.52～0.57, ΣREE 240.75×10－6 on averageand (La/Yb)N 8.88～9.41. According to geochemical characteristics and related discrimination diagrams, it is suggested that Yunxian granite should be of S type and its tectonic setting corresponds to CCG. The results of zircon U_Pb dating show that the formation period of the source rocks must not have been later than the Jinningian (＞778 Ma), with the main formation periods being from late Hercynian to Indosinian. Two ages of206Pb/238U and 207Pb/235U of the genetically magmatic zircon are 49 Ma and 61 Ma,which indicate the probable existence of Himalayan magmatic activity in Yunxian granite.