Abstract: In this paper, the influence of heavy metals Cu2+ (CuSO4·5H2O), Cr3+ Cr2(SO4)2·6H2O, Pb2+ Pb (CH3COO)2·3H2O on the activities of catalase, urease, phosphatase, sucrase of brown soil in Shandong were studied. According to the results of the experiments, put forward warning index and the threshold value of warning of soil enzyme for heavy metals Cu2+, Cr3+, Pb2+ pollution of Shandong brown soil. Under the conditions of the study, the pollution of Cu2+ could take catalase as warning index, according to corresponding regression equation, work out the threshold value of warning of Cu2+ critical concentration in environmental quality standard value for soils, first-class soil was 9.36% and the second was 11.57%; the pollution of Cr3+ could take urease as warning index, the threshold value of warning of first-class soil was 11.94%,that of second-class soil was 15.12%; the pollution of Pb2+ could take sucrase as warning index, the threshold value of warning of first-class soil was 1.50%,and the second-class soil was 3.42%.