Abstract: The previous studies of the Linxi Formation in Alukeerqin area show that the Late Permian Linxi Formation should be regarded as the most potential hydrocarbon layer as well as the most potential series of strata for exploration of the Upper Paleozoic in the middle-southern Da Hinggan Mountains; nevertheless, no further data are available concerning the determination of the deposition age of Linxi Formation. LA-ICP-MS zircon U-Pb dating of the intrusive granitic vein yielded an age of 242.0Ma±3.7Ma (MSWD=2.8, N=19), which implies that the emplacement of the dike occurred in the early period of Middle Triassic. The age can be used as indirect evidence of the upper limit of the sedimentation for Linxi Formation in this area.