Abstract: For violent vibration of the sink roll device of a hot-dip galvanizing line, an incomplete liquid-solid coupling method based on the wet modal was studied, the vibration modal of the device was numerically simulated, the natural frequencies and vibration modes were discussed, and the vibration test was performed. The partial mode of the sink roll changed the assembly relationship in bearings, and the clipping appeared in the time domain waveform of measured signals, indicating that crashing and friction existed in the sliding bearings. The frequency of the peak in the amplitude spectrum was 45.05 Hz, close to the fourth order frequency and mode, which showed that the fourth order natural vibration of the device was dominant. The double-frequency vibration was caused by nonlinear vibration of liquid-solid coupling. The main cause of sidebands near the peak in the amplitude spectrum came from the continuous action of the zinc liquid flow field. The numerical analysis and experimented research have significant correlation, and the incomplete solid-liquid coupling method can be effectively applied to engineering practice.