Air dense medium fluidized bed can achieve effective separation of -50 + 6mm coal. However, the bed characteristics significantly affect the separation behavior of coal particles. The results indicated that the bed critical expansion degree decreased with increase in static bed height, and the axial distribution coefficient of low-density particles increased from 0.798 at H-s=60mm to 0.950 at H-s=180mm with raising concentration of emulsified-phase particles, which revealed low bed height is advantageous for particles floatation, while bed density is not the main action factor in this process. As for bubble dimension calculation model, the Kato and Wen formula is favored for smaller relative error for 0.3-0.25 mm bed particles. In addition, separation was difficult when the density difference between the bed and the tracer spheres was more than 0.3 g/cm(3), and the lambda value was almost constant with increase in fluidization number for each sphere whose density difference was less than 0.3 g/cm(3). With increasing Delta rho from 0.07 g/cm(3) to 0.27 g/cm(3), the lambda values for d=38, 25, and 15mm increased from 0.44, 0.69, and 1.54 to 0.64, 1.00, and 2.01, respectively.