Biochar application has been suggested as an effective means in abating climate change by sequestering carbon. In this study, a 3-year field experiment was conducted to investigate the effects of biochars on soil organic carbon(SOC) cycling under laboratory incubation under different water conditions change. The results indicated that the dynamics of SOC mineralization preferably followed the first-order kinetics. Soil moisture affected SOC mineralization significantly. Under 25%WHC(water holding capacity), 50%WHC and 75%WHC moisture conditions, compared with C0(no biochar), the intensity of mineralization of SOC under C20(biochar, 20 t/hm~2) and C40(biochar, 40 t/hm~2) decreased by 28.57% - 42.86%(25%WHC), 22.22% - 33.33%(50%WHC) and 15.00% - 30.00%(75%WHC), respectively. There were significant differences in responses of microbial biomass carbon, soil organic carbon and metabolic quotient to the water regimes with Biochar addition. Biochar could keep the stability of the microbial biomass carbon and reduce SOC mineralization under low moisture content. Therefore, the results indicated that BC has the important significance for soil carbon sequestrating and maintaining the stability of soil organic carbon in agricultural soil.