The work aims to necessarily analyze the parameter vibration to improve the stability of the sprayer system as the problem of low spray efficiency and quality of the automatic sprayer is closely related to the vibration generated during the working process. Firstly, the bending-torsion coupled vibration model for the sine excitation cantilever beam of sprayer arm-spray gun system was established and the finite difference discretization of the system's parameter variation equation was conducted to obtain the mass and time-varying stiffness matrices of the system. Then, the time discretization and Matlab vibration toolbox was used for solution and analysis. The natural frequency of the sprayer system had a sinusoidal variation trend with the time, and it had a tendency to increase with the increase of excitation amplitude and frequency. When u>3 cm, the vibration amplitude of the system would increase sharply, indicating that the bending-torsion was divergent and the system tended to be unstable. When Ω>150 rad/s, it was unstable; when Ω<150 rad/s, most of the system tended to be stable, and the system was unstable near Ω=95 rad/s. The sprayer cantilever beam has complex vibration behavior under different excitation parameters. It is of great significance to study its vibration characteristics for improving the stability and efficiency of the automatic sprayer.