Abstract: In order to achieve uniform and precise control for spraying, The control system for spraying and test installation was designed, based on PWM. Opening frequency and duty cycle were adjusted by PWM to achieve Uniform Spraying. The frequency and duty cycle effect on uniform and cumulative quantity of spraying was found. The relationship between frequency, duty cycle, forward velocity and spray distribution coefficient of variation was found. The relationship was simplified by statistical method. Optimization of uniform spraying was achieved according to analysing this model. The reliability was tested by Repeated experiments, and precision was tested fitting.