In this paper, the application scope of the average flow model is extended to grease lubrication considering the non-Newtonian characteristics. First, flow factor expressions applicable to both Newtonian fluids and non-Newtonian fluids are derived. Then, a model problem is established by coupling the Reynolds governing equation, film thickness function, and boundary conditions and solved for the flow factor. Fit the result into empirical relations for conveniently using in the grease lubrication analysis. Finally, the influence of several parameters on the flow factor is studied. The results demonstrate that the film thickness ratio, rheological index, and surface elastic deformation have a significant effect on the flow factor, and the influence law is affected by the orientation of the surface roughness.