Abstract: Results of acute toxicity test of four pesticides for Daphnia carinata was reported in this paper. The results showed that 48 hours LC₅₀ values of Deltamethrin, Methylparathion, Lindane (γ-BHC ) and Carbo-furaa to that species were 0.000123; 0.013; 0.075; and 0.076 ppm respectively. The degree of toxicily may be arranged in the following order: Deltamethrin>Methylparathion>Lindane>Carbofuran. According to the application-coefficients of the toxicants derived from the LC₅₀ values of these chemicals and their dosages in farm the safety use of the four pesticides has been evaluated and discussed.