Abstract: In this work 168 samples of CWM were prepared from 14 kinds of Chinese coals and 12 dispersants, and the apparent viscosities of these CWM were measured by Haake RV 12 model Rheogeniometer at shear rate D=100 s^-1.Slurries formulated with different dispersants for the same coal or with the same dispersant for different kinds of coal showed obviously different results in the dispersibility and viscosity reduction. The relationship between relative apparent viscosity of CWM and volume fraction of coal in CWM was studied. The result showed that the experiential constant (k) in the Frankel equation was not only dependent on the geometrical distribution of particles but also on the coal properties, and an experimential relationship between constant (k) and coal properties was set up. Furthermore, the effect of interaction of complex coal particles on the apparent viscosity of CWM was discussed.