Abstract: In order to obtain the safe concentrations of 6 commonly-used aquaculture drugs and provide theoretical basis for the prevention and treatment of Masracembelue armatus diseases in the seeding cultivation and breeding,the acute toxicity of 6 commonly-used aquaculture drugs on juvenile Mastacembelus armatus with an average length of(7.65 ±1.03) cm and weight of(1.193 ±0.529) g was studied by a semi-static toxicity experiment method at the water temperature of 25~28℃.The results showed that the safe concentrations of avermectin solution,beta-cypermethrin solution,chlorine dioxide,symclosene,strong glutaral solution and ridomil were 0.308,0.027,0.491,0.041,4.598,and 1.053 mg/L,respectively.Conclusion:among the 6 commonly-used aquaculture drugs,symclosene should be banned to treat the disease of juvenile Mastacembelus armatus because its toxicity was the highest of all and its safe concentrations were significantly lower than the common concentrations.Fortunately,the safe concentrations of avermectin solution,beta-cypermethrin solution,chlorine dioxide,strong glutaral solution,and ridomil were near or higher than their common concentrations,so they could be used safely in treating the disease of juvenile Mastacembelus armatus.According to the evaluation standard of toxic substances to fish toxicity level,the toxicity of beta-cypermethrin solution and symclosene was high,while that of avermectin solution and chlorine dioxide was moderate,yet that of strong glutaral solution and ridomil was low.