Abstract: Tilapia was used as the experimental object, the effects of ultrasound-assisted infiltration of trehalose on the quality of freeze-dried tilapia fillets were studied. The pretreatment process conditions of ultrasonic-assisted infiltration of trehalose were optimized using single-factor experiments and response surface experiment with the comprehensive scores of rehydration rate, whiteness value, texture, and Ca²⁺-ATPase activity as indexes. The results showed that the optimum process conditions were ultrasonic power 450 W, ultrasonic time 55 min, trehalose concentration 90 g/L. Under these conditions physical and chemical indicators were:rehydration rate (0.5983±0.0060) g/g, whiteness value of 75.1287±0.2540, Ca²⁺-ATPase activity of (2.4997±0.0113) μmolPi/mgprot/h, hardness of (3.7433±0.0492) N, elasticity of (1.1753±0.0096) mm, adhesiveness (2.3373±0.0193) N and chewiness (1.6763±0.0082) mJ, all of which were optimized. The comprehensive score of freeze-dried tilapia fillet quality was 0.6229±0.0101, which was 1.74% less than the predicted value (0.6339) compared with the theoretical value. It showed that the ultrasound-assisted infiltration of trehalose was an effective method to improve the physicochemical quality of freeze-dried tilapia fillets.