Abstract: Aiming at environmental problems caused by insufficient use of chemical solutions in spray operation, a variable control spray system for precise pesticide was designed．System took a 32-bit microcontroller STM32F103ZET6 as core and constructed spray control system including upper computer, central controller, and sensor．Upper computer was used to receive spray amount set by user and displayed real-time information such as work speed, liquid level status, spray flow rate, and mechanical position．Spray performance experiment was conducted to verify system stability and spray uniformity, PID parameters that affect spray volume and stability were set．Determine proportional coefficient K_P range as 0.21～0.30, integral coefficient K_I as 0, and differential coefficient K_D as 0.1～1.0．Combination tests were conducted using adjusted K_P and K_D values with speeds of 0.9, 1.0, and 1.1 m/s．Optimal PID parameter combination was determined to be K_P=0.3、K_I=0、K_D=0.1, with system achieving maximum sprays medicine volume, nozzle sprays most stably, and spray volume adjusted with speed．Control system hardware and software design was reasonable and met design requirements．