Abstract: The rheological properties of dense-medium suspension in coal separation was related to the solid volume concentration and coal slime content. The prediction model was established by measuring the dense-medium suspension viscosity under different shearing rate to study the influence of volumetric concentration and coal slime content of medium suspension on rheological properties. The experiment results have shown dense-medium suspension viscosity increases with the increment of volumetric concentration under the given coal slime content. On the other hand, the viscosity decreases with the increment of coal slime content increasing under the given volumetric concentration. The predict model of the dense-medium suspension viscosity demonstrated that the lower limit of separation of dense medium separator is 13mm and coal slime content of dense-medium suspension should be less than 0.30.