Based on 1∶200000 regional geological mapping in the early 1970’s, the Erdaowa rock Group was named in Erdaowa area of north Hohhot, consisting of metamorphic conglomerate, schists and marbles and so on. According to the latest 1∶250000 regional survey results, the Erdaowa rock Group was subdivided into three sections from the bottom to top, including Hongshankou rock Formation, Halagenggou rock Formation and Dongliang rock Formation. In order to get new age constraint for the Erdaowa rock Group, SHRIMP UPb dating of zircons from the biotite—amphibole schist of the Dongliang rock Formation was carried out by the authors of this paper. The data show the following age: 1890±8 Ma, interpreted as the formation age of biotite—amphibole schist, the intermediate—basic volcanics of the upper part of the the Erdaowa rock Group. Combined with the available age data, it is concluded that the Erdaowa rock Group formed in the Paleoproterozoic(1800~2400Ma).