Located in northern Songpan-Garzê orogenic belt and intrudinginto Triassic Xikang Group mainly comprising sandstone and slate, the Hongyuan granites are composed of medium-fine grained granodiorite and monzogranite. Geochemical analyses show that they have high SiO2 (62.36%～73.7%) and Al2O3 (13.84%～16.69%) content, low TiO2 (0.18%～0.72%), Na2O (2.64%～4.43%) and K2O (2.24%～5.07%) content, and similar Na and K content.These granites are of metaluminous-peraluminous high-K calc-alkaline series and can be mostly classified as I type granite (some Yanggonghai and Dagaizhai granites can be classified as A type granite). Their total REE amounts vary considerably (84.39×10-6～241.07×10-6). Light REE elements are of relative enrichment. They are enriched with large ion lithophile elements such as Ba, Rb and Th and depleted in high field strength elements like Nb and Ta. In chondrite_normalized REE patterns，all samples are LREE-enriched with insignificant Eu anomalies (δEu=0.54～1.28). Light and heavy REE are significantly fractionated. The fractional extent of light REE［(La/Sm)N=6.13～11.16］ is higher than that of heavy REE ［(Gd/Yb)N=2.13～9.52］LA-ICP-MS U-Pb zircon ages (211.0±0.11 Ma) of the granites suggest that their intrusion occurred in late Indosinian. The melt composition is different in different source positions. It is thought that these granites most likely resulted from partial melting of the homologous crust, and that there was a substantial proportion of biotite in the source region because they were metaluminous-peraluminous high-K calc-alkaline granites with high SiO2 and Rb content and relatively high K2O/Na2O ratio. They were probably derived from metamorphic greywacke and intermediate volcanic rocks. Based on Hf－Rb/10－Ta×3 triangular diagram and Rb－(Y+Nb) discrimination diagram, the authors have reached the conclusion that the granites might have been formed in an collision environment after the main intracontinental collision and required an underplating or intraplating scheme of mantle-derived magma.