The transport velocity of a coarse particle in a Multi-Solid Fluidized Bed (MSFB) consisting of particles different in size and density was measured using an acoustic technique. Effects of the solid circulating rate of fine particles on the diameter of coarse particles were studied. The equation for calculating the transport velocity was established considering the collision characteristics between the fine and coarse particles, The transport velocity of coarse particles obtained by solving the related equation demonstrated a good agreement with those obtained from the experimental data. The calculated results for air-fine 50 mm and 100 mm particles coincided with the experimental results within 20% and 34% errors, respectively. Experimental results obtained in a lab-scale MSFB with a diameter of 0.05 m showed that the transport velocity of coarse particles decreased with increasing the solid circulation rate.