Abstract: In order to make full use of oyster shell resources and turn waste into treasure, the ultrasonic-assisted preparation of calcium lactate as a food additive from oyster shell was studied in this paper, and the technology was also optimized. By taking the yield and content of calcium lactate as the indexes of evaluation, the effect of four factors including the acid-solid ratio, liquid-solid ratio, ultrasonic temperature and ultrasonic time on the yield and content of calcium lactate prepared from oyster shell was studied by using the single factor experiment. On the basis of the single factor experiment, combined with the orthogonal experiment, the optimal process conditions for the ultrasonic-assisted preparation of calcium lactate from oyster shell were optimized. The results showed that the effect of each factor on the yield and content of calcium lactate was the acid-solid ratio, liquid-solid ratio, ultrasonic time and ultrasonic temperature in order. The optimum process conditions the ultrasonic-assisted preparation of calcium lactate from oyster shell were as follows:acid-solid ratio of 1.6:1, liquid-solid of 12.5:1, ultrasonic temperature of 65℃, ultrasonic time of 45 min. Under the optimum process conditions, the yield and content of calcium lactate prepared were (72.81±1.47)% and (84.79±0.88)% respectively, showing that the yield and content of calcium lactate prepared from oyster shell under the optimum process conditions were high, and the operation method was simple, which could be popularized and applied in the production.