In this study, artificial waste was used to investigate the impact of bed particle-size distributions (narrow, flat, and Gaussian) on heavy-metal distributions in the particles in the bottom ash during defluidization in a fluidized bed incinerator. When the particle size was less than 0.500 mm, the heavy-metal concentration within the particles tended to increase, and when the particle size was greater than 0.850 mm, the heavy-metal concentration showed a substantial increase. With regard to heavy-metal capture, the formation of the low-melting eutectic complexes was produced by the combination of heavy metals with Na. The capturing effect of the liquid eutectic material may be a more important mechanism than adsorption. The comparison of heavy-metal concentrations at different particle-size distributions showed that heavy-metal concentrations in large and small particles with narrow particle distributions and their total retention rates were higher than the corresponding values in the case of flat and Gaussian particle distributions.