Acute toxicity of heavy metals( mercury, cadmium lead, chromium and copper ), organophosphours insecticides( EPN, 2, 4- D, and parathion ), and other chemicals( arsenic, cyanide, and phenol ) to Daphnia magna was analyzed. Acute toxicity of heavy metals, organophosphours insecticides and other chemicals on Daphnia magna, LC$_{50}$ was showed 0.07-0.73mg/1, 0.22-1.94mg/t and 1.73-39.92mg/1 respectively. Daphnia magna to most of toxic chemicals was sensitive and then it seems to be useful except phenol in toxic test of water. Toxic chemicals were classified as Group 1 which had a high LC$_{50}$ value and the low increase rate of toxicity according to the increase of concentration, Group 2 which had a high LC$_{50}$ value and the high increase rate of toxicity, Group 3 which had a low LC$_{50}$ value and the low increase rate of toxicity. To Daphnia magna, lead, chromium, EPN, and parathion were included in Group 1; Mercury and copper in Group 2; Arsenic and cadmium in Group 3; Cyanide 2,4- D, and phenol in Group 4.