Abstract: This paper reports four zircon U-Pb ages of granitoids in Darhan Muminggan Joint Banner, Inner Mongolia. Two granodiorite samples from Bater magmatic arc in the northern part and two granite samples from a single pluton in the southern part were dated by LA-ICP-MS zircon U-Pb method so as to define their emplacement ages and provide constraints on the subduction and collisional events of the Paleo-Asian Ocean in the central part of Inner Mongolia. The two granodiorite samples yielded zircon U-Pb ages of 468Ma±2Ma and 452Ma±3Ma, respectively, indicating that the southward subduction of the paleo-Asian ocean beneath the North China Craton started at least at 468Ma, which resulted in the formation of Bater Obo magmatic arc, and the two granite samples gave zircon U-Pb ages of 268Ma±2Ma and 264Ma±2Ma, respectively, which are within the range of pre-existing age data from the western pluton, although the tectonic setting of the Middle Permian plutonism in the southern part is still uncertain.