Acute toxicity of heavy metals( Mercury, Cadmium, Lead, Chromium and Copper ), Organophosphorus insecticides( EPN, 2, 4- D, and Parathion ), and other chemicals( Arsenic, Cyanide, and Phenol) to Daphnia magna, and Vibrio fischeri was analysed. Daphnia magna to most toxic chemicals was most sensitive among test organisms alld then Daphnia magna seems to be more useful in toxic test of water. Daphnia magna was more sensitive to heavy metals than insecticides and other chemicals. The sensitivity of Visrio JircAeri to heavy metals was not so different from that to insecticides and the sensitivity to other chemicals was low. Visrio JircAeri appears to be more sensitive to toxic chemicals than Photobacterium phosphoreum, which was compared as recorded values of P.phosphoreum. Toxic chemicals were classified as Group 1 which had a high $EC_{50}$ or $LC_{50}$ value and the low increase rate of toxicity according to the increase of concentration, Group 2 which had a high $EC_{50}$ or $LC_{50}$ value and the high increase rate of toxicity, Group 3 which had a low $EC_{50}$ or $LC_{50}$ value and the high increase rate of toxicity, and Group 4 which had a low $EC_{50}$ or $LC_{50}$ 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 : Arsonic and Cadmium in Group 3 : Cyanide, 2, 4-B, and Phenol in Group 4. To Visrio JircAeri, Lead, Chromiurl 2, 4- D, and Parathion were included in Group 1 : Merecury, Cadmium and Arsenic in Group 2 : Cyanide in Group 3 : EPN, Copper, and Phenol in Group 4.