Concentrations of pollutants will increase if sewage sludge is applied to soil, thus posing a risk to the health of human. An incubation experiment was carried out with results showing that concentrations of EDTA and CaCl₂ extracted Cu and Zn in the sludge-amended soils increased with time and reached to maximum 150 days after the incubation. The average concentration of EDTA-extracted Cu and Zn was 30.0 mg kg^-1 and 30.1 mg k^-1, and increased by 21.4 mg kg^-1 and 26.1 mg kg^-1 over the control, respectively. The average concentration of CaCl₂ extracted Cu and Zn was 0.11 mg kg^-1 and 3.65 mg kg^-1, about 0.10 mg kg^-1 and 3.37 mg kg^-1 higher, respectively, than in the control. Application of sewage sludge into the soil posed a potential risk of heavy metal pollution. Soil type, sludge characteristics and application time should be taken into account simultaneously for reducing the risk of heavy metal pollution of the soil in making agricultural use of sewage sludge.