[Objective] To investigate the effects of land use and cover change（LUCC）on carbon stocks of specific soil types in northeast China. [Methods] Based on the obtained soil organic carbon（SOC）stock data and land cover data from 1990 to 2020，ArcGis was used for spatial analysis to extract long-term cropland and land type conversion periods. LUCC dynamics and their influencing mechanism on SOC stocks were analyzed. [Results] 1）From 1990 to 2020，the study area generally maintained as a carbon source，with SOC stocks decreasing by 0.046 Pg. Specifically，SOC stocks in croplands and wetlands decreased by 0.111 Pg and 0.007 Pg， respectively，while those of other land-use types declined by 0.313 Pg. In contrast，SOC stocks in grasslands and forests increased by 0.102 and 0.283 Pg，respectively. 2）Long-term cultivation resulted in a loss of 0.341 Pg of SOC stocks. Reclamation of natural lands（forests and grasslands）led to SOC losses of 5.79% and 4.32%，respectively. 3）Land-use changes were mainly reflected in a decrease in cropland area（11 917 km² ）and an increase in forest and grassland areas（1 535-4 213 km² ）. Wetlands decreased by 1 185 km²，primarily occurring in Inner Mongolia and Heilongjiang（89.00%）. 4）The decreased cropland area was mainly converted into grasslands（64.00%） and other land types（29.00%），with meadow soil，dark brown soil，and chernozem being the main soil types. Wetland loss mainly occurred in black soil and meadow soil regions，while the conversion of other land-use types into forests and grasslands primarily involved dark brown soil（15.00%-41.00%）and meadow soil. [Conclusion] Changes in SOC stocks in northeast China are mainly driven by natural land reclamation and long-term cultivation，as well as the policies of returning croplands to forests and grasslands and the demand for ecological restoration. In the future， efforts should be strengthened to restore croplands and wetlands and to protect forests and grasslands in Heilongjiang，so as to enhance SOC stocks.