The Zalantun region, located in the middle part of the Erlian- Hegenshan- Heihe suture belt, contains well- developed early Late- Paleozoic granitoids superimposed by ductile deformation. Through field investigation and systematic analyses, such as microscopy, geochemistry and zircon U- Pb geochronology, we investigated rock- forming chronological sequence, petrogenesis and tectonic setting of the granitoids, redefined the time of their deformation, and then further revealed amalgamation between Erguna- Xing’an and Songnen blocks, providing new materials for understanding the regional tectonic evolution of the Xing’an- Mongolian Orogenic Belt. Geochronological study shows that the early Late- Paleozoic magmatism in the Zalantun region happened during 405~325 Ma, and can be sub- divided into three periods: Stage I at the Early- Middle Devonian (405~380 Ma), stage II at the Late Devonian- initial Early Carboniferous (365~350 Ma) and stage III at the late Early Carboniferous (335~325 Ma) respectively. TheⅠ stage and Ⅱ stage granitoids belong to metaluminous to weakly peraluminous granitoids of shoshonite series and high- K calc- alkaline series, and are likely the I- type and high fractionated I- type granites formed in island- arc magmatism of subduction environment. And the Ⅲ stage ones belong to metaluminous to weakly peraluminous granitoids of middle to high- K calc- alkaline series, and are likely high fractionated I- type and A- type granites formed in magmatism of post- collisional environment. The universal deformation of the granitoids, which was the product of lateral escape in a post- collisional environment, occurred in the end of Late Carboniferous to Early Permian (308~290 Ma). We conclude, therefore, that the occurrences of the early Late- Paleozoic granitic magmatism in the northern Great Xing’an Range was related to the collision and combination between Erguna- Xing’an and Songnen blocks, and the amalgamation at the Zalantun region might occur in the middle Early Carboniferous.