We selected forest, grassland, wetland ecosystems to estimate the status of vegetation and soil organic carbon sequestration capacity and changes in ecosystem carbon sequestration between 1990 and 2010. Then, we projected the potential for ecosystem carbon sequestration under three different social development situations up to 2030. The past, current, and future potential of carbon sequestration services for mainly terrestrial ecosystems were assessed. (1) In 2010, carbon sequestration of mainly terrestrial ecosystems was 17.29 PgC in China, of which vegetation carbon was 8.7 PgC and soil organic carbon was 8.59 PgC at a depth of 30 cm. Forest carbon accounted for 73.26%; grassland carbon, 21.55%; and wetland carbon, 5.18%. (2) Between 1990 and 2000, carbon sequestration services of mainly terrestrial ecosystems increased slightly, and overall carbon sequestration reduced by 2.15%; forest, grassland, and wetland carbon decreased by 1.12%, 0.97%, and 20.19%, respectively. Between 2000 and 2010, carbon sequestration services of mainly terrestrial ecosystems increased slightly, and the amount of carbon fixed increased by 2.92%; forest carbon increased by 3.72%, and grassland and wetland carbon decreased by 0.62% and 5.59%, respectively. (3) When the former 10 years were compared to the latter 10 years, carbon sequestration services of mainly terrestrial ecosystems showed a shift from a slight drop to a slightly upward trend. The variation trends of carbon sequestration services for forest changed from decreasing or basically unchanging to increasing. Grassland carbon sequestration services continued to show a basic balance and a decline in the proportion of carbon sequestration. The reducing trend of wetland carbon sequestration services has improved. (4) Up to 2030, carbon sequestration services of main terrestrial ecosystems will show an obvious rising trend, (up to 430.11-498.06 TgC), with an increase of 5.15%-5.97% in the proportion of carbon sequestration.