Abstract: An experiment was conducted to investigate the effects of growth years of alfalfa on the enzyme activity and nutrient in soil for proposing that soil enzyme activity could be considered as one of the most important indexes to indicate soil fertility. The results of this study showed that the enzymes activity of nutrients in soil every soil layers with different growing years was significantly higher or lower than that of control (P0.05). The enzymes activity of urease, catalase and peroxidase were correlated with soil fertilities, implying that the activities of enzymes could be used to indicate the changes of soil fertility and sensitiveness of soil biology. The activity of polyphenol oxidase was not strongly correlated with soil nutrients.