Abstract: To analyze the effects of non-Newtonian lubricants and surface roughness in journal bearing lubrication,a modified Reynolds equation is derived.In the equation,differential viscosity and the first normal stress function are defined to specify the rheological properties of non-Newtonian medium,flow factors are used to specify the effect of surface roughness.Modified Reynolds equation is numerically calculated using super over relaxation method.Numerical results of lubrication show that differential viscosity is the principal non-Newtonian properties affecting lubrication,it is determined by material parameters of lubricant and is affected by shearing rate.Under the effect,load capacity of non-Newtonian lubricants is not always higher or lower than that of Newtonian lubricants'.Effect of the first normal stress difference increases under dynamic load.Surface roughness shows obvious effect on load capacity when it is greater than 1/10 film thickness,and surface with longitude pattern affects load capacity most.However,surface roughness takes less effect on lubrication than lubricants' non-Newtonian property does.