The shear viscosity of carbon black–polybutadiene, styrene suspensions is studied. The suspensions show strong shear thinning behavior. At very low shear rate, an extrapolated constant shear stress that is designated as the apparent yield stress can be obtained. A model is developed based on the kinetics and energy dissipation of the flocculation process in suspensions of Newtonian liquid. With a mixing rule, the model can also predict the viscosity of suspensions with particle-size distribution. The applicability of the model can be extended to suspensions of non-Newtonian liquid if the parameters in the model are regarded as functions of the viscosity of suspending liquid.