| A field experiment was conducted to study the seasonal variations of soil enzyme activities (urease, alkaline phosphatase, sucrase, amylase, cellulose and catalase) in alfalfa field with different growing years (0, 3, 4, 5, 7, and 10 years) in arid desert oasis, and the purpose was to provide a theoretical basis for cereal-forage rotation system. Results indicated that different cropping years for alfalfa had effect on the activities of soil enzyme. In comparison with fallow farmland, the activities of soil enzyme were increased in various cropping years. The activities of urease, sucrase, and cellulose increased, and then decreased, and then increased with the increase of cropping years, but the activities of amylse, alkaline phosphatase, and catalase increased and then decreased with the increase of cropping years, the activities of soil enzyme was the highest in five-years alfalfa, and was increased by 80.56%,69.91%,46.75%,533.33%,110.71%, and 11.81% in 0～60 cm depth compared with the CK, respectively. The activities of soil enzyme decreased significantly with the increase in soil depth, being mainly concentrating in the 0～20 cm depth. The activities of urease and amylase were the highest in the summer, the activities of sucrase, cellulase, catalase, and alkaline phosphatase were the highest in the spring. In addition, there existed significant correlations among the five kinds of soil enzymes except sucrase. |