The BaoerhantuBainaimiao arc magmatism occurred along the southern margin of XingMeng Orogenic Belt (XMOB) and is considered to have been formed by the Early Paleozoic subduction between PaleoAsian Ocean and North China Block. It is the key area to reconstruct the tectonic history of the Central Asian Orogenic Belt (CAOB). However, most of previous studies focused on the intrusive rocks and volcanic rocks from the Bainaimiao Group in eastern arc with limited attention given to the volcanic rocks from the Baoerhantu Group in western arc. In this study, we present petrological investigations as well as geochronological, geochemical and Hf isotopic data for the volcanic rocks from the Baoerhantu Group in northern Damao Banner, to discover their petrogenesis and envisage the Early Paleozoic tectonic evolution of XMOB. The volcanic succession can be classified into the intermediatebasic and intermediatefelsic sequence. Zircon LAICPMS UPb dating shows that the age of the dacite is 447. 3±2. 5 Ma, which means Late Ordovician. Geochemically, all the volcanic rocks are generally enriched in LILE (e. g. Rb, Ba, Th, U) and LREE, depleted in HFSE (e. g. Nb, Ta) and Ti, with weak negative Eu anomalies, which is similar to the island arc or active continental margin magmatite. Petrological and geochemical characteristics suggest that the intermediatebasic rocks were generated in island arc setting and formed by partial melting of a mantle wedge from a lithospheric mantle metasomatized by subducted slabderived melt, with involvement of sedimentary material in the source. The intermediatefelsic rocks have obviously low Nb/U values（1. 45~3. 63） and positive zircon εHf(t) values (+2. 2~+11. 0 ) indicating that the magmas were derived from juvenile basic lower crust and metasomatized by subduction slab fluids. Combined with previous studies and recent research results, the intermediatefelsic rocks have depleted Hf isotopic compositions with twostage model age (tDMC) of 1637~839 Ma, indicating a Precambrian basement for the Baoerhantu Arc, which has tectonic affinity with the north margin of North China Block. Accordingly, our research demonstrates that the southern margin of XMOB belongs to an active continental margin in early Paleozoic, formed due to the southward subduction of the PaleoAsian Ocean beneath the north margin of North China Block. In the meanwhile, the BaoerhantuBainaimiao arcrelated magmatic belt was formed.