Mylonitized granite in the AilaoshanJinshajiang tectonic zone is hosted in the center of the Ailaoshan high grade metamorphic belt. LAICPMS UPb dating of two zircon samples (08Q222 and 08Q215) shows the ages of the growth rims of zircon grains are 250.2±2.1Ma（MSWD＝2.5）and 247.2±2.3Ma（MSWD＝0.15）, respectively. The lattice preferred orientations by EBSD suggest that the caxis fabrics of quartz are prism slip, and the ductile deformation formed under the condition of amphibolite facies (500~630℃）. This temperature is far lower than the zircon crystallized temperature (675～864℃) in magmatism and the closed temperature (＞800℃) of UPb system in zircon, so the deformation and metamorphism can not destroy the UThPb stabilization of zircon grains crystallized during magma intrusion. The features of zircon Cathodoluminescence images and the UPb concordia lines of zircon indicate that the LAICPMS UPb dating (247～250Ma) for zircon rims represents the emplacement age of granite. The granite is characterized geochemically by peraluminous minerals (e.g. muscovite), low Na and high K, A/CNK and A/NK＞1.0, similar distribution of REE and trace elements geochemistry similar to those in the upper crust, as well as strong enrichment of largeion lithophile and magmatophile elements, depletion of Sm and Y. Tectonic discrimination diagrams of (Yb+Ta)Rb, (Y+Nb)Rb, CaO(TFeO+MgO) and Cenozoic subducting collision of the AilaoshanJinshajiang tectonic belt all suggest that the granite formed and emplaced during the stage of collision. Combined with mylonitized granites successively discovered in the Ailaoshan and Dianchangshan high grade metamorphic belt by previous workers, and ductile deformation and metamorphism of felsic rocks occurring in the middlelower crust (deeper than 10~15km), our study shows that the AilaoshanJinshajiang metamorphic belt was the early Triassic or early rocks which were squeezed out and uplifted to the crust after it was subducted to the lower crust and suffered ductile deformation and metamorphism. Therefore, the strong metamorphism might occur in Mesozoic or Cenozoic, but not Proterozoic, and is not or completely the crystalline basement rock of Yangtze block.