Erosion processes of disturbed and undisturbed soils were studied by simulated rainfall experiment Results showed that sediment concentration for undisturbed soil decreased first and then fluctuated,while sediment concentration for disturbed soil increased first,then decreased and fluctuated at last.At the sam slope gradient and rainfall intensity,sediment concentration for disturbed soil was greater than that for urdisturbed soil.In early stage,sediment yield for undisturbed soil was greater than that for disturbed soil whereas in late stage,sediment yield for disturbed soil was greater.The time when sediment yield for undi:turbed soil is greater than that for disturbed soil was advanced with increased slope gradient.After a stead state was reached,eroded sediment rate of disturbed soil was greater than that of undisturbed soil and th gap between disturbed and undisturbed soils became larger with increased slope gradient.