Urban expansion is one of the features of urban development that has caused many ecological and environmental problems. Evaluating the impact of urban expansion on carbon sequestration of the urban forest is important to understand the carbon cycle in urban ecosystems. Multiple remote sensing data were used to map land covers and carbon sequestration indicators of Shenyang in 2000, 2005, and 2010. Urban land area percentage (UAP), urban expansion magnitude (UEM), net primary productivity (NPP), aboveground biomass (AGB), and the change rate of NPP (RNPP) and AGB (RAGB) were analyzed in regions with different distances from the urban core. Results showed that the decline of UAP and bimodal fluctuation of UEM was found as the increase of distance from urban center. Urban forest NPP and AGB both rose with distance from urban center increased. Significant differences in NPP and AGB existed in various urban forest types. Moreover, UAP was significantly negatively correlated with NPP and AGB. We conclude that urban forests see more disturbances compared to natural forests. The evergreen coniferous forest has the highest ability of carbon sequestration, and great potential of carbon storage is found in the urban forest. Besides, the urban forest’s carbon sequestration function will be maintained when adopting appropriate urban development mode.