According to the turbulence theory and the behavior characteristics of the grains, the instantaneous velocity of fluid around the bed surface is regarded to accord the normal distribution and the finally movement status probability of grains on the bed surface are obtained. By the principle that the status probability implicates the coming behavior tendency, the equilibrium bed height calculation model is evolved, which can be used to simulate the bed moving process visually in horizontal solid-liquid two phase flow with wall fluid plus filtration, minus filtration and no filtration to judge whether slugging would occur or not.