Abstract: Using simulated acid rains of pH values at 2.0, 3.0, 4.0 and 5.6, acute toxicity experiments were conducted on wheat seedlings to investigate the seedlings catalase spectrophotometry(CAT)and superoxide dismutase(SOD)activity by means of UV detection. The results showed that: CAT and SOD had the highest activity when the pH value was controlled at about 3 in wheat seedlings; under the stress of simulated acid rain with different acidity conditions, the dose-effect relationship curve of CAT and SOD activity takes aunimodal curve, and the peak value can be considered the threshold value of the toxic reaction of wheat seedlings exposed to acid rain. Conclusion: simulated acid rains of different acidity have different CAT and SOD enzyme induction on wheat seedlings