Abstract：The pr oblem of low separation efficiency and blocked water distributor was studied by the combining method of theory and experiment, and optimum operating parameters werefound. Research shows, when the suspension density is 1.4, 1.5, 1.6, 1.7 g/cm³ respectively, for the 13～6 mm feeding particles:the required minimum flow velocity of upward water is 0.63～1.14 cm/s. The optimal ratio between horizontal and vertical flowrate is 2.0～2.5 (ρ=1.4 or 1.5 g/cm³) and 1.5～2.0 (ρ=1.6 or 1.7 g/cm³) ;the optimum feeding position is vertical ratio equals 0.7 between height Hiabove the water distributor and the suspension height H₀, and the horizontal ratio belongs 0.1～0.3 of distance Lifrom the feeding port and length L₀ of sorting chamber; Under the optimal conditions, the Ecart probable moyen is 0.097, 0.071, 0.068 and0.089 g/cm³ and the ash content is 8.55%, 8.87%, 9.15% and9.54%, respectively.

Keywords：heavy medium vessel; slack coal separation; rising water