When the control signal of the proportional directional valve is superimposed with the fixed amplitude and frequency flutter signal, the valve core will increase with the opening degree, and the amplitude value of the displacement tremor will attenuate, the phenomenon are studied. Firstly, the mathematical model of the proportional directional valve was built according to the dynamics equation of the valve core, which includes the analysis of the friction force between the valve core and the valve body at the gap and the valve cavity with the Newton internal friction law; secondly, the model was simulated using AMESim software. With the increase of the opening of the valve plug, the displacement amplitude value of the displacement tremor appeared attenuation, and the attenuation was nonlinear. Finally, the factors influencing the attenuation were further explored. The results show that under different valve opening degrees, the friction force changes nonlinearly, and the hydraulic force and the spring force are basically a linear change, and it is concluded that friction is the main factor that causes flutter attenuation.