Abstract: Calcium propionate is a common food preservative. In order to reduce the production cost of calcium propionate, the waste oyster shell was used as the main raw material to prepare the calcium propionate by using the economic and efficient ultrasonic assisted method, in order to transform the waste oyster shell into treasure. The effects of the four factors including the ratio of acid to solid, the ratio of solid to liquid, ultrasonic temperature and ultrasonic time on the yield and content of calcium propionate prepared from oyster shell were studied by means of the single factor and orthogonal experiments, thus to determine the optimal technological conditions for the preparation of calcium propionate from oyster shell by using the ultrasonic assisted method. The results showed that the effects of various factors on the yield and content of calcium propionate were in order as follows:the ratio of liquid to solid, the ratio of acid to solid, ultrasonic time and ultrasonic temperature. The optimal technological conditions for the preparation of calcium propionate from oyster shell by means of the ultrasonic assisted method were as follows:the ratio of liquid to solid of 22.5:1, the ratio of acid to solid of 2.1:1, ultrasonic temperature of 55℃, and ultrasonic time of 120 min. Under the optimal technological conditions, the yield and content of calcium propionate prepared were (89.79±0.11)% and (97.95±0.19)%, respectively. Therefore, the preparation of calcium propionate from oyster shell by means of the ultrasonic assisted method was not only easy to operate, but also could effectively improve the comprehensive utilization rate of oyster shell resources, which could be popularized and applied in production.