Abstract: The acute toxicity of dichlorvos(DDVP) on tadpoles of Calluella yunnanensis was studied with standard determination technique of aquatic biological toxicity.It was showed by the results that the 24 h,48 h,72 h and 96 h LC₅₀ values of dichlorvos to the tadpoles was 114.82 mg/L,102.33 mg/L,81.28 mg/L and 51.29 mg/L respectively under 21~22 ℃ temperature condition.There was a linear correlation between the effect duration and DDVP concentration,and the safe concentration(SC) was 5.13 mg/L.DDVP had remarkable influence on tadpoles of Calluella yunnatnensis,but there was no obvious dosage-effect relation at abnorrnal behavior of the tadpoles and DDVP concentration.