Abstract:Objectives: Wunuer area,Great Hinggan Mountains( Daxing’an Mountains), Inner Mongolia is a part of the accretion zone of the Paleozoic continental margin of the southeast Siberian plate,where the syenogranite is widely found, it is essential to carry out geochronological study and petrogeochemical analysis for better understanding of the syenogranite. Methods: On the basis of detailed field work,the petrogeochemical testing and LA- ICP- MS zircon U- Pb dating age are carried out on the syenogranite Results: LA- ICP- MS zircon U- Pb age 310.8±2.5 Ma(MSWD=1.6),belongs to Late Carboniferous. Petrogeochemical researches indicate that the granite belongs to high- K calc- alkaline, the granite is peraluminous granite with A/CNK=1.03~1.08. The granite is enriched in Rb, Th, depleted in Ba, Sr and Nb, Ti; is enriched in LREE and relatively depleted in HREE, with obvious negative Eu anomaly (δEu=0.36~0.90).Petrogeochemical analysis shows that the granite has the characteristics of S- type granite. Its source rock is continental crust and it is from partial melting of continental crust mudstone. The initial magma temperature is 700~750℃,the initial magma pressure is 0.15~0.2GPa. Conclusions: Comprehensive studies indicate that the granite is formed in the closing of the Paleo Asian Ocean , which provided new constraints and a supporting instance on the close time of the Paleo Asian Ocean and tectonic evolution of the northeast China block group.