Abstract: The purpose of this study is to evaluate the effects of mineral floatation reagents on Daphnia. The toxicity of eight kinds of floatation reagent was studied under renewed static conditions at 25±1℃. The 48hr LC50 of floatation reagents for 12±12h old Daphnia magna Straus was estimated to be between 2.40 and 102.30 mg/L. The acute toxicites are in the order of MPANo.2 oilFu0145YxS808Ganbian oilNo. 10 oil. Chronic No-Observed Effect Concentration(NOEC)of mineral floatation reagent 0145 was 2 mg/L and Lowest-Observed-Effects Concentration(LOEC)was 3 mg/L. The application factors were within the range of 0.15-0.22. The test of toxicity of phosphoromineral dressing effluent to Daphnia carinata King indicates that the toxicity is low. The iso-toxic units of four mineral dressing reagents were calculated to be 50.00 for S808, 26.67 for sulfitating soap, 6.66 for Na2CO3 and 0.35 for Na2SiO3, respectively. A classification of the toxicity of chemicals to Daphnia is proposed as: very high, 0.1(×48 LC50); high, 0.1-1; moderate, 1-10; low, 10-100; slight or non-toxic,100.