A three‐dimensional fractal structure model was introduced to quantify the morphology of inclusion clusters, and the floating behavior of different inclusion clusters was simulated directly using lattice Boltzmann method to investigate the effect of morphology on the floating velocity in molten steel. It is found that the morphology, which can be described quantitatively by fractal dimension has a significant effect on the floating behavior of inclusions. The terminal floating velocity of inclusion clusters is smaller than that of spherical inclusions, which consist of same number of primary particles. The ratio between the floating velocity of inclusion clusters and that of spherical inclusions decreases with the increasing primary particle number. By introducing the fractal dimension, an equation for the floatation velocity of cluster‐shaped inclusions is derived from the simulation results.