Abstract: Experiments were conducted to study permeation-enhancing effect of various concentration of water soluble azone,propylene glycol and menthol on the in vitro percutaneous penetration of trichlorfon through hybrid snakehead skin Channa maculate(♀)×Channa argus(♀),and selected the suitable penetration enhancers for trichlorfon used in aquaculture.Franz diffusion chambers were used and excised hybrid snakehead skin was chosen as transdermal barrier.GC method was established to determine the content of drug in receivers at specified time points.The in vitro permeation effects of every combination of trichlorfon with various concentration enhancers were evaluated through calculating and comparing the cumulative penetration amount of per unit area(Q),the rate of percutaneous absorption(Js),permeability coefficient(KP) and enhancement ratio(ER).The results revealed that propylene glycol and low concentrations of water soluble azone had the permeation-enhancing effect,the sequence of effect was 1×10-2 propylene glycol >6×10-7 propylene glycol >6×10-7 water soluble azone(V/V).However,1×10-2 water soluble azone(V/V) showed antagonism at certain times;1 mg/L and 2 mg/L menthol had little influence on the permeation-enhancing effect.