Abstract: The molten salt fluid-particles transition state is modelled using KTGF-based TFM and CFD-DEM in fluidized beds. The solid phase constitutive equations are modelled using a low density ratio KTGF model. The normal and tangential forces of discrete particles are simulated using CFD-DEM. Two-equation model is used to characterize molten salt fluid turbulence. Wavy-like flow near the bottom and aggregates/fluid voids flow at the upper part coexist along bed height. The molten salt fluid pressure drops and dominant frequencies of wavy-like flow using TFM agree with simulated results using CFD-DEM. The simulated transition state from TFM and CFD-DEM coincides with predictions using four different criteria in literature. The effect of molten salt temperature on normal and tangential Reynolds stresses is discussed. The predicted expansion height and water volume fractions using TFM and CFD-DEM agree with experimental data in an ambient water fluidized bed.