By using simulation method, this paper studied the effects of furadan on the activities of soil urease, invertase and alkaline phosphatase, with the affecting factors investigated. The results showed that after adding furadan into soil, soil urease activity was decreased first but increased then, indicating that the ecotoxicity of furadan was reduced gradually. When the concentration of furadan was less than 0.3%, soil urease, invertase and alkaline phosophatase were all activated, and in some soil samples, a significant positive correlation was observed between soil invertase activity and furadan concentration, suggesting that soil invertase activity could be used as an indicator for the soil pollution caused by furadan. It was concluded that the quality of soil and ecological environment would be kept safe under low concentrations of furadan (< or = 0.3%).