Abstract: In this paper, the existence of 508-471 Ma Early Paleozoic granites is confirmed by using the whole rock-mineral separate Rb-Sr method and LA-ICP-MS zircon U-Pb dating method. Based on their petrology and geochronology, the Early Paleozoic granites may be subdivided into three rock associations, i.e.: gneissic granodiorite-monzogranite associated with high-grade metamorphic rocks (508±15 Ma), massive granodiorite-monzogranite (499±1 Ma) and alkali-feldspar-alkaline granite (471±3 Ma). The successive occurrence of the three granite associations suggests that the tectonic evolution experienced syn-collisional to post-collisional extension, implying that a collisional orogenic event took place in the eastern Xiao Hinggan Mountains in the Early Paleozoic.