Based on survey and research, the authors have found a suite of Neo-Archaean intrusive rocks composed of plagiogranite, quartz diorites, and diorites in Seerteng area, Inner Mongolia. Isotopic dating of plagiogranite indicates that the age of the rocks is at 2 400~2 500 Ma. According to isotopic age and regional geo- logic characteristics, the authors hold that the intrusive rocks might be products of Neo-Archaean