Toxicity of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate on soil sucrase activity was studied by laboratory simulation method, and the kinetics and thermal parameters of enzyme catalyzed reaction were also investigated. Results showed that the activation effect of ionic liquids on the soil sucrase activity was found in short term, and the activation effect was better with higher concentration of ionic liquid. But in the long term, activation-inhibitory-activation effect was found in higher concentration rather than the lower concentration (10 mg/kg) with the activation effect in the whole incubation process. Kinetic parameters, Km and Vmax were changed a certain in different concentrations of ionic liquids due to the changes of the affinity of enzyme to substrate. The optimum temperature of enzymatic reaction was about 320 K, and thermodynamic research showed that highest activation energy (Ea) and activation enthalpy (⊿H) were found in controls, which indicated that the addition of ionic liquid to soil was favorable for the producing of enzyme-substrate complexes.