Abstract: Mengyang granodiorite intrusion is located in Mengyang area of Tengchong block, western Yunnan Province. LA-ICPMS zircon dating indicates that the granodiorite was emplaced at 115.2±1.0Ma. The granite mass was formed in the Early Creta-ceous. Geochemical data show that the granodiorites has the following data:SiO₂=62.39%~67.97%, Na₂O+K₂O=6.26%~7.80%, K₂O/Na₂O=0.45~1.11, rich in Si, Na, poor in P, MgO=1.78%~1.98%. Mg#=34.90~48.40, thus belonging to metaluminous to weakly per-aluminous, calc alkaline series. It has both the characteristics of I-type granite and S-type granite in the granodiorite and also has the characteristic of magma mixing. It has Sm/Nd ratios of 0.12~0.20, is enriched in Th, Rb, Ba, Pb and U, and depleted in Ta, Nb, Zr, Hf and Ce, thus similar to features of calc-alkaline rocks in island arc or active continental margin. According to geochemistry and trace element discrimination diagrams for tectonic interpretation, the Early Cretaceous granodiorites are considered to be of the post-collision type formed in a island arc tectonic setting. The granodiorite was from the mixing of mantle-derived magma and par-tial melting crust. The early Cretaceous intrusive rocks in the Tengchong block were intimately related to the closure of the Bangong Co-Nujiang-Longling-Ruili ocean basin and were formed by the subduction of ocean crust and the collision between the Tengchong block and the Zuogong-Baoshan block.