Abstract: In order to improve the problems of environmental pollution and chemical residue caused by pesticide waste during the spraying operation of maize crops, a sub-controlled variable spray control system was designed. The STM32single-chip microcomputer was used as the control core of the system,collecting the travel speed of the tool and the actual spray pressure at the upper and lower nozzles of the lifting rod with the pressure sensor and speed sensor, through the method of artificially giving the theoretical pressure value by the user, the single-chip microcomputer compared the relationship between the actual pressure value and the theoretical pressure value and then adjusted the opening of the electric control valve at the upper and lower nozzles of the lifting spray rod, so as to realize the spray pressure at the upper and lower nozzles of the lifting rod with the travel speed change spray. The results were obtained by constructing physical tests as follows: the average relative error of upper nozzle spray flow was 2. 59%, the average relative error of lower nozzle spray flow was 2. 87%, and the average relative error of upper nozzle spray flow and lower nozzle spray flow in variable speed test was 2. 6% and 3. 11% respectively. The test results show that the software and hardware design of the control system are reasonable, and the control accuracy can meet the requirements.