The bedrock exposed badly in Honghuaerji area in Ewenki Autonomous Banner in Inner Mongolia. Geological work degree is low. Intrusive rocks found in the former work were classified into middle Carboniferous period. Through zircon SHRIMP U Pb dating of plagioclase granite which was newly discovered in regional geological survey work with the scale of 1∶50000, the age was gained as 172.2±1.3Ma and classfied int middle Jurassic intrusion. It is conducted that Honghuaerji plagioclase granite was formed by Mesozoic subduction and collision between medium and small blocks in Neoproterozoic period, then meltted after joining depleted mantle materials.