In this paper, viscosity profiles of solutions of blend polymers were studied. These solutions were made up with incompatible polystyrene and poly(methyl methacrylate) in chloroform as a cosolvent. A totational viscometer was used to obtain the viscosity data. And the data were analyzed by using the Ree-Eyring flow equation. The parameters in the Ree-Eyring equation could be expressed as fuctions of blending ratio $\chi$. The activation free energy for flow of a blend system is expressed by a combination of the activation free energies of the component polymers. Thus $\beta_{i,b1}$ which is proportional to the relaxation time of the ith flow unit of the blend system, can be expressed as an exponential fuction of $\chi$. Another parameter $(1/\alpha)_{1,b1}$ which is the intrisic shear stress of the ith flow unit, can be expressed by a linear combination of 1/$\alpha_i$ for each component in terms of $\chi$. And a remaining parameter $x_{i,b1}$ the area fraction occupied by the ith flow unit in the blend system, can also be expressed by a linear combination of $x_i$ for each component in terms of $\chi$. Introducing these considerations, we derived a new viscosity equation for the blend system. The experimental data of $\eta_{b1}$ were compared with the calculated $\eta_{b1}$ values with good results. This equation can also explain very well such a phenomenon that shows constant viscosities over the low shear rate region for high blending ratio of poly(methyl methacrylate).