Abstract: Intermediate fluid vaporizer (IFV) is one of the key equipments at floating LNG maritime terminal stations. Due to the effect of sea wind and waves, the liquid level fluctuation inside the IFV can impact the heat exchange performance of the equipment. In this paper, the unsteady sloshing boundary conditions were worked out by Fluent calculation software according to 3D numerical simulation method. Then, the sloshing motion of the liquid in the intermediate fluid chamber inside the IFV was simulated. And finally, the effects of sloshing amplitude, sloshing frequency and intermediate fluid filling level on the fluid level fluctuation in the intermediate fluid chamber were analyzed. It is shown that the safe filling level of intermediate fluid is 50% when sloshing angle is in the range of 3°-10°and sloshing frequency is in the range of 0.1- 1 Hz. The fluctuation of intermediate fluid level becomes more and more intense with the increase of sloshing angle and the decrease of sloshing cycle. The research results provide the reference for safe LNG transportation.