The healthy Carassius auratus fries were used for the acute toxicity of four antibacterial drugs(Pefloxacin,Florfenicol,Thiamphenicol,Equindox) at water temperature of 22 ℃~25 ℃.The half lethal concentration(LC50) in 24 h,48 h,96 h were determined,at the same time,safe concentration(SC) also were determined.The results showed that the half lethal concentration(LC50) in 24 h were 1 935.98,1 314.14,1 265.03,135.46 mg/L,respectively;the half lethal concentration(LC50) in 48 h were 1 863.62,1 154.23,177.05,130....