[Aim] The widespread use of the herbicides in paddy fields may have some negative effects on Procambarus clarkii under the freshwater crayfisho-rice co-culture system.[Method] Acute toxicity of three amides herbicides (etochlor, proxychlor and butochlor) on P. clarkii was studied using semi-static laboratory procedures to calculate the safe exposure concentrations (SC) and analyze the median lethal concentrations (LC₅₀) attenuation law.[Result] The crayfish lay on its side, the motion frequency of pereiopods and pleopods decreased, and finally died with the increase of exposure time and drug concentration. The LC₅₀ (96 h) and SC of acetochlor, pretilachlor and butachlor in crayfish were 0.0707 and 0.0146 mL·L^-1, 0.0119 and 0.0021 mL·L^-1, and 0.0073 and 0.0014 mL·L^-1, respectively. The LC₅₀ declined with increased exposure time duration after 96 h of exposure, which basically meets hyperbola model. The regression equations were as follows:y₁=2.0840x^-0.7380 (R²=0.9973); y₂=0.1106x^-0.4930 (R²=0.9872); y₃=0.2236x^-0.7480 (R²=0.9990). The sensitivity of three herbicides in crayfish from highest to lowest was butachlor, pretilachlor and acetochlor.[Conclusion] Under the conventional dose, acetochlor and pretilachlor could be used in the freshwater crayfisho-rice co-culture system, while butochlor might have a greater risk in conventional doses.