Abstract: Effects of cyhalothrin with different concentration on urease and catalase activities in tobacco planting soil were analyzed by lab simulation. The results showed that urease activity was significantly influenced by cyhalothrin, and could be described as a process of activation→inhibition→reinstation→re-activation. But the effect of cyhalothrin on catalase activity was not obvious. Compared with the control group in early training (1~5 d), only 1.0 mg/kg of cyhalothrin had obviously influence on catalase, but the general trend performed as the process of activation→inhibition.