In this paper,the activities of enzymes (catalase,polyphenol oaidase,invertase,crease,alkaline and neutral phosphatases) in black soils with different fertility and the correlations between enzymatic activities on the one hand and soil humic substances and other elements of fertility on the other hand are discussed.It has been shown that:1.Among six kinds of enzymes tested,most of the enzymes have significant correlation with soil organic matter or its components.Their activities can be used as an index to characterize the contents and status of organic matter.Polyphenol oxidase has negative significant correlation with C/N and humic acid/fulvic acid.Its activity characterizes the humification degree of humic substances.The activities of various kinds of enzymes characterize specifically or compositely the soil carbon,nitrogen and phosphorous status,cation exchange capacity and aeration status.In addition,there are some definite correlations among various kinds of soil enzymes.