Abstract: The theoretical and numerical simulation research on dense medium separation involves the rheological properties of suspensions. The apparent viscosities in different conditions of dense-medium suspension were determined to study the influence of density,volumetric concentration and coal slime content on the rheological properties of medi- um suspension used in coal preparation. Linear fitting method was used to reduce the effect of particles sedimentation when measuring the apparent viscosity by the rotational viscometer on the range of density 1. 45-1. 80 g / cm3 and coal slime content 0 - 0. 30. The experiment results show that the dense medium suspension used in coal preparation is pseudoplastic fluid. When the volumetric concentration is constant,consistency coefficient decreases approximately lin- early,and power law exponent increases with the increment of coal slime content. Under the condition of constant coal slime content,consistency coefficient increases approximately linearly,and power law exponent decreases with the vol- umetric concentration increasing. The equations for calculating consistency coefficient and power law exponent were put forward under the general conditions in industrial application of dense medium coal preparation respectively,and the relative deviation of the approximate formulas is less than ±10% .