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At present, the vacuum precooling device has a large volume, high energy consumption, and the water catching capacity of the water trap can not be well adapted to the problem of evaporation of water vapor. In order to solve the above problems, a smallscale wolfberry vacuum precooling device based on brine storage was designed. According to the technical requirements, the mathematical model of vacuum precooling was established. The theoretical analysis of the surface mass transfer resistance layer was carried out. The key parameters of the vacuum pump, vacuum precooling and cooling load, brine storage system and computer detection system were designed and calculated. Finally, a small cooling storage vacuum precooling device for fresh wolfberry with stem was produced. The experimental results showed that the vacuum precooling device can reduce the center temperature of 8.714kg fresh wolfberry to the preservation temperature of 4.0℃ in 879s, and the water loss rate was 5.29% when the water replenishment rate was 4.50%. The water trap of the device was designed to have a water catch rate of 75.00%, and the actual water catch rate was 79.32%. The brine temperature in the brine tank was increased from -20.1℃ to -9.8℃ during the test. The cold storage capacity of the brine in the tank can ensure the smooth completion of the vacuum precooling process. By adjusting the brine pump to change the brine circulation speed, the balance between the catchment of the water trap and the evaporation of water vapor was achieved, which met the design requirements.