Urban expansion has an impact on ecosystems and results in the loss of ecological lands. The occupation of ecological lands includes two processes:directly by urban expansion, and indirectly because of the compensation for croplands that are lost during urbanization. Many researches have discussed the direct impact of urban expansion on ecosystems; however, most of them have ignored the impacts of cascading processes of urban expansion and cropland reclamation. Therefore, we have explored the impacts of the cascading processes of urban expansion and cropland reclamation on the ecosystem of a carbon storage service in Hubei during 2000-2015 by means of the GIS spatial analysis method and InVEST model. The results show that during 2000 and 2015:(1) the reduction of carbon storage resulting from the impacts of cascading processes of urban expansion and cropland reclamation was 40.90 Tg; (2) the indirect impact from cropland reclamation accounted for 31% of reduction of carbon storage. Our study indicates that the main cause of carbon storage decrease is the impact of the cascading processes of urban expansion and cropland reclamation. Furthermore, ignoring the impact of cropland reclamation can lead to an underestimation of the decrease of carbon storage.