Abstract: The Cailong pluton is located in the southern rim of the Gangdise-Nyainqentanglha slab, near the Yarlung Zangbo junction. With analysis on the petrography, REE and trace element of samples, it is revealed that the pluton falls into marginal phase, transitional phase and intermediate phase. Being genetically I-type granite, the rock-forming magma of the pluton might have resulted from the mixture of basic magma at the bottom of the lower crust or crust-mantle boundary and acidic magma of the lower crust formed by partial melting. Formed in continental arc environment, there were favorable conditions for mineralization such as the hydrous minerals of biotite and hornblende, with high-silicon, enriched calcium and low-alkali, rich Cl and poor F, medium to strong enrichment of Ag, Cu, Mo and Sn. The Pb and Zn mineralization in E-W-trending fracture zone shows that the pluton has the potential of forming mesothermal deposit.