Abstract: Yi’ershi granite located in the middle of Daxing’anling area, about 260 km². It consists of three phase intrusions, the middle-fine grained adamellite, coarse-grained grained porphyritic orthoclase granite and coarse-grained orthoclase granite, respectively. Pluton intruded into the Carboniferous-Permian strata, and the Late Jurassic volcanic rocks are unconformably overlying them. Zircon LA-ICP-MS U-Pb dating ages of the pluton is (226.3±1.4) Ma, indicates that the Late Triassic granite. The granitoid has the characteristics of high silica, alkali-rich, low calcium, belongs to the weakly peraluminous rocks. Total REE abundance is variable, rich of HREE, and the fractionation of LREE is more than that of HREE relatively, and by obivious Eu anomalies. Strong incompatible elements are enrichment, lack of Ba, Sr, P and Ti. Overall belong to the transition series from high-K series to calc-alkaline series granite, shows the characteristics of typical post-orogenic granite (POG). It mainly formed in the transition phase from the extrusion orogenic to extensional regime tectonic environment, which suggesting the collision orogeny between Siberian Plate and North China Plate affected by continued to Triassic in the region.