Effects of cadmium (Cd) on microbial biomass, activity and community diversity were assessed in a representative variable charge soil (Typic Aquult) using an incubation study. Cadmium was added as Cd(NO3)2> to reach a concentration range of 0～16 mg Cd/kg soil. Soil extractable Cd generally increased with Cd loading rate, but decreased with incubation time. Soil mi-crobial biomass was enhanced at low Cd levels (0.5～1 mg/kg), but was inhibited consistently with increasing Cd rate. The ratio of microbial biomass C/N varied with Cd treatment levels, decreasing at low Cd rate (