Abstract: In order to obtain the bubble separation behavior in the swirl vane separator of the molten salt reactor quantitatively, the liquid flow field distribution inside the separator was obtained by computational fluid dynamics method. Based on the bubble separation model that coupling the vortex model and interphase force, the numerical calculation program of bubble motion was developed to quickly predict the critical separation diameter of the bubble in the molten salt medium in the separator. By quantifying the force acting on the bubble, the separation mechanism of the bubble has been demonstrated. The analysis indicates that the interphase force of the bubble closely relates to the position of different radius in the separator. The virtual mass force and drag force acting on the bubble in the axial direction determine the bubble separation length. When pressure gradient force, lift force, drag force as well as virtual mass force acting on the bubble reach a balance in the radial direction, it can no longer centripetally move into the air core and be captured and separated.