Aiming at the problems of the difficulty of decontamination of radioactive pollution in the narrow areas and the existence of great security hidden dangers during nuclear energency rescue, the research on the improvement of small decontamination spraying machine is carried out, and the control system of spraying machine is optimized. The system is controlled by PLC and uses the touch screen as the site control terminal.After modifieding the control of the petrol engine , the signal acquisition of gasoline engine is emphatically solved, and the overall circuit design is introduced. The control syetem is tested by single step, and the experimental results show that the syetem is operating normally with accurate status diaplay, and the man-machine interface is friendly and easy to use.