The regional air quality modeling system RAMS-CMAQ (Regional Atmospheric Modeling System and Models-3 Community Multi-scale Air Quality) was developed by incorporating a vegetation photosynthesis and respiration module (VPRM) and used to simulate temporal-spatial variations in atmospheric CO2 concentrations in East Asia, with prescribed surface CO2 fluxes (i.e., fossil fuel emission, biomass burning, sea-air CO2 exchange, and terrestrial biosphere CO2 flux). Comparison of modeled CO2 mixing ratios with eight ground-based in-situ measurements demonstrated that the model was able to capture most observed CO2 temporal-spatial features. Simulated CO2 concentrations were generally in good agreement with observed concentrations. Results indicated that the accumulated impacts of anthropogenic emissions contributed more to increased CO2 concentrations in urban regions relative to remote locations. Moreover, RAMS-CMAQ analysis demonstrates that surface CO2 concentrations in East Asia are strongly influenced by terrestrial ecosystems.