Abstract: The change in urease activity in 4 types of paddy soil, i.e. percogenic paddy soil, submergic paddy soil, sandy clay soil and gleyed paddy soil, was studied. And the relationship between the activity of urease and the efficiency of urea in the soil types was analysed. Results showed that the urease activity of soil types was different from each other’s, and changed with soil profile,season, method of fertilizer application, number of urease-producing microorganisms as well as the total nitrogen of soil. Of the 4 soil types, percogenic paddy soil had the highest urease activity and the lowest efficiency of urea; gleyed paddy soil had the lowest urease activity and the highest efficiency of urea; submergic paddy soil lay between the above two in both the activity of urease and the efficiency of urea.The change in urease activity in different paddy soil showed a tendency that activity was higher in early cropping season than in late cropping season; in top soil layer than in low soil layer.The soils where urea or other fertilizers was applied with organic manure increased their activity of urease as compared with the control treatment.