Abstract: In order to obtain the optimum conditions of LiF-NaF-KF(FLiNaK) molten salt decontaminating by combination of ultrasonic and chemical method, response surface methodology and Box-Behnken design(BBD) are used to establish a polynomial model. The influences of different reaction temperature, ultrasonic wave power, the concentration of aluminum nitrate, and reaction time were explored. The determination coefficient(r²) and adjusted r²_adj of model are 0.958 0 and 0.915 9, respectively, which indicates the models has good agreements with experimental data. Results indicate that the impacts of factors on removal rate from strong to weak are reaction time, ultrasonic wave power, reaction temperature and the concentration of aluminum nitrate. The model predicts removal rate of molten salt of 99.99% with optimal condition of 60 ℃ of reaction temperature, 300 W of ultrasonic wave power, 0.1 mol/L of aluminum nitrate concentration and 9 min of reaction time. The experiment is carried out under the predicted optional condition, and the removal rate of 98.74%±1.12%(n=3) is obtained, and the average relative errors is 1.25%. The result can give reference for the next engineering applications.