Abstract: In order to solve the problems of slow precooling speed and high energy consumption of existing lychee origin precooling devices, a mobile lychee storage and spray precooling device control system was designed to improve the guarantee of post-harvest precooling effect of lychee. The system mainly consisted of STM32 main control system, pump driving system, refrigeration system, data acquisition system and auxiliary control system. The intelligent serial screen interface was designed based on USART HMI software. The intelligent serial screen communicated with STM32 microcontroller through TTL serial port, which can complete the setting of lychee spray precooling parameters and display the operation status information of the control system to realize the accurate control of lychee spray precooling device. The test hardware platform was built to evaluate the precooling effect with the test factors of spray flow rate of water pump and load of lychee at single spraying, and the precooling time and uniformity of lychee as the test index. The test results showed that before 1/2 precooling time（HCT）, when the spray flow rate exceeded 70 L/min, the spray flow rate had little effect on the cooling rate; after HCT, the precooling time was reduced by 170 s（90 L/min）, 260 s（110 L/min） and 262 s（130 L/min）, respectively, compared with that under 70 L/min, so that when spraying flow rate was more than 110 L/min, the effect of increase of spraying flow rate on the lychee cooling rate was not significant; test on different loads of lychee found that when the lychee load was greater than 50 kg, increasing the lychee load has a significant effect on the lychee cooling rate; when the lychee load was 50 kg, the uniformity of the lychee precooling completed with the increase in spraying flow first become larger and then reduced; when the spraying flow was 90 L/min, the uniformity of lychee precooling increased and then trended to stabilize with the increase of lychee load. The research results can provide help for the optimization of the control system of lychee spraying precooling device to achieve rapid precooling of lychee after harvesting, so as to protect the lychee after harvesting.