Abstract: In order to solve the problem of low screening efficiency caused by the accumulation of materials at the feeding end of a flip-flow screen, a four-mass variable amplitude flip-flow screen consisting of one main frame and three floating frames is proposed. The transfer function method is used to obtain the expressions of the amplitude and phase of the main and floating frames; The amplitude and phase -frequency characteristic curves of the main and floating frames are plotted, the effects of changing the mass of the frame and the stiffness of the spring on the dynamic characteristics of the screen are analyzed. The amplitudes of the three floating screen frames on the working frequency were adjusted by the multi-objective optimization algorithm, so as to make the materials experience the varying vibratory amplitudes during the screening process. The results show that: The size of the four resonance frequencies are determined by the mass of the screen frames and the stiffness of the springs; the stiffness of the shear springs mainly affects the second, third and fourth-order resonance frequencies, while the stiffness of the vibration isolation springs mainly affects the first-order resonance frequency; In the process of designing a four-mass screen, the multi-objective optimization algorithm can be used to choose the appropriate parameters, so that the amplitude ratio of the three floating screen frames can reaches the preset value at the working frequency.