The origin, source characteristics and dynamic background of the Early Paleozoic magmatic rocks in the Erguna massif are of great significance for revealing the tectonic evolution history of the restoration area. In this paper, the Early Paleozoic intermediate-basic complex in the upper reaches of Pangu River in the Northern of Great Xing’an Range was selected for petrology and zircon U-Pb chronology and petrogeochemical analysis. Field investigation and laboratory study show that the rock types of the complex are mainly hornblende gabbro and gabbro, rare quartz diorite, diorite, pyroxenite, olivine gabbro and other intermediate rocks or ultrabasic rocks. The dating results show that the formation age of the hornblende gabbro is 479.2±2.1Ma, indicating that the complex was formed in the Early Ordovician. In terms of geochemical composition, the Early Paleozoic intermediate-basic complex rocks in the upper reaches of the Pangoo River have SiO2 contents ranging from 40.74% to 54.95%, Fe2O3^T contents ranging from 3.99% to 14.66%, MgO contents ranging from 3.36% to 17.78%, Mg^# values ranging from 47 to 79, which are (high potassium) calc-alkaline series rocks, relatively enriched in light rare earth elements and depleted in heavy rare earth elements with δEu from 0.77 to 2.06. Furthermore, they are relatively enriched in large ion lithophile and radioactive elements such as Rb, Ba, U, K, Pb and Sr, and depleted in high field strength elements such as Nb, Ta and Ti, which is similar to the geochemical characteristics of arcmagmatic rocks in subduction zone. The magma was originated from partial melting of mantle dominated by subduction fluid metasomatism supplemented by sediment melt metasomatism. The source area is dominated by spinel bearing garnet lherzolite, and a small amount of spinel lherzolite, which experienced different degrees of crystallization differentiation in the rising process. Combined with the regional lithostratigraphic data, comprehensive analysis shows that the Early Paleozoic intermediate-basic complex in the upper reaches of Pangu River was formed in the tectonic environment of continental extensional zone (or initial rift), which is probably related to the lithosphere extension background after the collision between the Siberian plate and the Erguna massif.