As the key equipment to control the pressure stability of the coolant system, the pressurizer plays a role in maintaining the primary system pressure in the reactor. During the operation of the sea-based reactor, the internal free liquid level of the pressurizer will fluctuate greatly with different marine cycles, causing additional acceleration in the horizontal or vertical direction, which will cause the water level measured by the differential pressure measurement method to deviate from the actual water level. It will adversely affect the judgment and control of the signal. Moreover, the fluctuating liquid level will frequently trigger the water level alarm signal, resulting in the submersion of the sprinkler tuber and the exposure of the electric heating rod, which will reduce the safety and economy of the reactor. Therefore, this research is aimed at suppressing the fluctuation range of the water level and correcting the deviation of the water level measurement so as to improve the inherent safety of the reactor. In the present study, the experimental system consists of a motion excitation drive mechanism and an optical system. The experimental system has successfully established sloshing phenomenon of the pressurizer under different forms of motion by Laser induced fluorescence (LIF) technique and the experimental results obtained are compared with numerical results. The results of the research show that the pressurizer can make significant free surface fluctuation when excitation close to the natural frequency of the pressurizer. The suppression model developed by FLUTENT can effectively reduce the fluctuation range of free liquid level. In addition, the deviation of water level measurement enlarges with the swing angle increasing. The deviation can be reduced to the allowable error range by means of angle correction.