Abstract: The biotite monzogranite intrusive body in northern Jarud, Inner Mongolia, located in the eastern section of Daxinganling Mountains, was formed in Late Triassic Period. The rock is geochemically characterized by rich SiO₂, Al₂O₃ and alkalis, with Na₂O/K₂O less than 1, A/CNK between 1.021 and 1.084. The LREE and HREE are notably fractionated, with enriched LREE. The Eu negative anomaly is obvious. The trace elements show depletion of Ba, Sr, Ti, P, Eu and Yb, with the geochemical characteristics of A-type granite. Combined with regional geological data and previous research, it is supposed that the biotite monzogranite was formed in crustal stretch thinning setting of late orogenic epoch within the plate.