Based on numerous eapariments, the optimal drying cnnditi。二for flavouring fillet of filefish were found, i. e. the temprature of fillet=380g, air flow rate about 3.3m/s and the humidity of drying medium.The surFace temperature t, of fillet performs a predominate effect during the whole drying pro.The surface water activity Axv, of fillet plays an important role in the drying speed, the quality of the product and the degree of dryness can be cal- eulated from t,. Moreover,adopting the temperature of drying medium tD, the wet bulb temperature ty and the surface temperature t, the degree of dryness may be enn- trolled and determined as well. During the drying process the surface water aotivity Aw, fluctuates with the variation of air humidity accordingly. It demonstrates the variation of humidity from 20%to 50 %RH will not significantly effect the drying time.