The relationship between the concentration of dimehypo and soil urease activity parameters was studied in this paper. The results showed that the characteristics of soil urease had remarkable divergence among the tested soils from different ecological zones. Dimehypo inhibited soil urease activity very significantly and the characteristic parameters of soil urease, such as its activity, maximum reaction velocity V_max, V_max/K_m and velocity constant kexcluding K_m, were decreased with increasing dimehypo concentrations. The correlation of urease activity and dimehypo concentration was in very significant level with few exceptions. To a certain extent, urease activity can be used as an index to characterize the soil polluted by dimehypo. The enzymatic reaction mechanism was mixed-inhibitory between soil urease and dimehypo. It was concluded from ED₅₀ values that the high content of organic matter as well as total N and total P alleviated the ecological toxicity of dimehypo in soils.