Abstract: Soil enzymes directly affect the material circulation and energy flow in artificial grassland ecosystem, it is an index to evaluate the quality of soil biological activity. Soil samples were collected from the artificial alfalfa grassland and farmland in agro-pastoral transitional zone, through the determination of soil organic matter, pH, available nutrient elements (N, K, Ca, Mg, etc.) content and activities of 4 soil enzymes (urease, alkaline phosphates, catalase and sucrase), the author analyzed the influence of soil physic-chemical properties on soil enzyme activities under artificial alfalfa grassland and farmland. The results showed that: (1) in artificial alfalfa grassland, the activities of soil urease and alkaline phosphatase had the same variation trend, the activities reduced obviously with the increase of planting year, and a significant difference was between varieties (P＜0.05), the average soil enzyme activity had an order as follows: 3 years＞6 years＞10 years grass; the activity of catalase increased gradually with the increase of planting year and there was significant difference between varieties (P＜0.05); (2) soil enzyme activities were different among different types of farmland, the activities of soil urease and alkaline phosphatase of maize field were only 24% and 70% of that of potato field; (3) by comparing the soil enzyme activities in artificial grassland and farmland, these enzyme activities (urease, alkaline phosphatase and catalase) were in the older of potato field＞3 years Ameristand grassland＞ maize field≥3 years Ladak grassland＞6 years Ladak grassland＞6 years Ameristand grassland＞10 years Ladak grassland≥10 years Ameristand grassland; (4) the results from correlation analysis showed that there were significantly negative correlations between urease, catalase and alkaline phosphatase, significantly positive correlation between sucrase activity and pH, significantly negative correlation between urease, alkaline phosphatase and pH, significantly negative correlation between available nitrogen and total nitrogen, and significantly positive correlation between catalase and organic matter, available nitrogen, total nitrogen and water soluble magnesium.