Abstract: The operating environment of floating nuclear power plants is definitely different from that of land nuclear power plants, which should be taken into account in the design of special safety facilities. Especially in the design of the facilities involving liquid flow,  the effect of marine environment adaptation under the ship’s motion exciting should be considered. Taking the pressure suppression pool as an example in this paper, finite volume method (FVM) is adopted to conduct simulation analysis for the motion process to study the water level change in extreme working environment and the differences with and without swash plate. Research results show that the lowest water level due to roll and pitch motion is lower than the initial water level. Resonance period of pressure suppression pool is not the same with the ship’s rocking period, thus the water level change mainly depends on the motion amplitude and structural members inside jointly.