Abstract: The effects of Cd,Zn,Cu and Pb loads on fractions of the metals in five soils were studied,and buffer capacity of the soils to heavy metals was analyzed.The major fractions of heavy metals in the unpolluted soils were residual forms,which accounted for more than 51% of the total metals.With increasing loads of heavy metals in the soils,the proportions of metals as exchangeable form increased,those as residual form decreased,and thus increased availability of the metals and their impacts on the environments.The interactions of metals with soil components varied with metal types.The buffer capacity of soils to heavy metals decreased in the order of Pb>Cu>Zn(>>)Cd,and lower in the acid and sandy soils.When heavy metals were input in low levels,the metals were preferentially transformed into oxides-and organic matter bound fractions.However,the metals were transformed into exchangeable and carbonate bound fractions when metals were input in higher levels.The proportion of exchangeable fraction of Cd,Zn,Cu and Pb in the soils increased and buffer capacity of the soils to the metals decreased with decreasing pH.