This study, taking the soil amended with sewage sludge taken from the Northern Wastewater Treatment Plant (Shenyang, China) as research object, investigated the dose-response effects of sewage sludge on chemical form distribution of Cd, Pb, Cu and Zn in soil. Moreover, the bioavailability of different forms of heavy metals in soil amended with sewage sludge was studied by means of Perennial Ryegrass pot experiment. The soil samples amended with sewage sludge with a sludge dosage rate of 0、9.1%、16.7%、28.6%、37.5%、44.4% and 50% (dry weight basis) were designated as CK、S₁、S₂、S₃、S₄、S₅、S₆, respectively. The chelated form, acid-soluble form, exchangeable form and bound form in neutral condition, alkali-soluble form and protein-binding form of heavy metals in soil amended with sewage sludge were extracted with 0.05 mol/L EDTA, 0.1 mol/L CH₃COOH, 0.01 mol/L CaC1₂, 1 mol/L CH₃COONH₄, 0.05 mol/L NaHCO₃ and 0.05 mol/L Tris-HCl, respectively. Results showed that the relative content of the chelated form of heavy metals in soil amended with sewage was the highest, accounting for 20.3%-40.0%, followed by alkali-soluble form and bound form in neutral of heavy metals. The contents of the exchangeable form in neutral, alkali-soluble form and protein-binding form of heavy metals were relatively low. The accumulation of Cd, Cu and Zn in ryegrass was found to increase with increase in sludge dosage rate. The highest content of Cd, Cu and Zn in ryegrass roots was observed with a sludge dosage rate of 44.4%, which was 0.3、2.3 and 6.5 times higher than those at control(CK), respectively. In contrast, the accumulation of Pb in ryegrass decreased with the increase in sludge dosage rate. A decrease of 40% in Pb content in ryegrass roots was observed with a sludge dosage rate of 37.5% as compared to the control. In order to assess the bioavailability of metals, correlation analysis using SPSS statistical software was performed to investigate the relationship between the total accumulation of heavy metals in ryegrass and contents of available forms of heavy metals in soil amended with different sludge dosage rate. The results of Pearson correlation coefficient analysis showed that a significantly (P<0.01) positive correlation was found between the contents of chelated form of Cu and Zn and plant accumulated metals. The content of heavy metals in ryegrass had significantly positive correlations with the content of Cu and Zn bound form under neutral condition in soil amended with sludge. There were power functions with positive coefficients relationships between the contents of Cd and Zn in ryegrass and the contents of acid-soluble form of Cd and Zn in artificial soil. Whereas, significantly (P<0.05) negative correlation was observed between Pb content in ryegrass and available forms of Pb content. The overall correlation data showed that the contents of heavy metals existing in the chelated form, acid-soluble form and bound form under neutral condition in soil amended with sludge correlated with the contents of heavy metals in ryegrass, suggesting that the three available forms of heavy metals might be absorbed and used by ryegrass. Therefore, contents of chelated form, acid-soluble form and bound form under neutral of heavy metals could be used as the indicator of bioavailable fraction in soil amended with sewage sludge.