Abstract: The lubrication equations involving surface fractal characteristics have been established by introducing surface fractal dimension D in the conventional lubrication equations, based on an analysis of the relationship between the surface roughness and the fractal characteristics of the material. Thus the variations of the pressure flow factor and shear flow factor determined the present equations with the surface fractal dimension D are theoretically investigated and compared with that based on the conventional lubrication equations. The disadvantages of the conventional lubrication equations describing the pressure flow factor and the shear flow factor are analyzed. The surface fractal parameters of SAE52100 steel were measured with a Talor 6 profilemeter. By analyzing the relationship between the surface roughness and the fractal characteristics, the obtained fractal dimensions are introduced into the expressions of the pressure flow factor and the shear flow factor. Thus, the lubrication equations involving surface fractal characteristics are obtained. In the process of analysis of the relationship between the above factors and D, for simplification, one relatively moving surface is assumed to be absolute flat and the oil film thickness is assumed to be 1 mm. The calculation results reveal that at a fixed fractal dimension D, both the pressure flow factor and shear flow factor increase with increasing length to width ratio of a representative asperity. They experience more irregular and significant variation and show local maximum and minimum values of higher resolution with increasing D, as compared with the variations with oil film thickness to roughness ratio. The present results may be referenced to reasonably selecting of lubricated surfaces.