Abstract: To design a fast brining technology for low-salinity tilapia (Oreochromis mossambicus) fillets, we compared four brining methods (standing brining, saline injection, vacuum brining, ultrasonic-assisted brining) on tilapia fillets quality (salt content, water content, weight changing rate, pH, proteolysis index, texture property). Besides, on the basis of single factor experiment of saline injection and with response surface methodology, we studied the effects of salt concentration, brining time and ratio of fillet mass (g) to brining liquid volume (mL) on the salt content of the saline injection fillets, and then optimized the process. The results show that the saline injection fillets had the best brining effect with high salt permeation rate, good product quality and high product yield rate. The single factor experiment indicates that salt concentration, brining time and ratio of fillet mass (g) to brining liquid volume (mL) were the main influencing factors. The conditions optimized by Box-Behnken design are as follows:salt concentration of 2.26 mol·L^-1, brining time of 2.5 h, ratio of fillet mass (g) to brining liquid volume (mL) of 1:3.4. Under these conditions, the actual salt content was 2.93%, and the relative error of the target prediction value was 2.39%, showing feasibility of this optimization.