The toxicity of herbicide-butachlor to four species of spiders(Pirata subpiraticus,Pardosa pseudoannulata,Tetragnatha maxillosa,Ummeliata insecticeps)collected from the rice fields was tested by the dipping method and raising in the experimental room.Then the effect of butachlor at low concentration on the growth and development of P.subpiraticus was investigated in the laboratory.The results showed that high-concentration herbicide-butachlor was strongly toxic to the spiders and the LC₅₀ order of butachlor to spiders was P.pseudoannulata>P.subpiraticus >T.maxillosa>U.insecticeps.And U.insecticeps was the most sensitive to the butachlor,LC₅₀ reached 9.616 05 mg/L.Butachlor also had significant influence on the body weight,survival rate and life history of P.subpiraticus.Compared with the blank,the body weight and the rate of female to male of P.subpiraticus were significant.Generally,the butachlor prolonged the development for 10 d of P.subpiraticus,and decreased the survival rate to 43.4%.