In this paper, a viscosity modification model is developed which can be applied to describethe thin film lubrication problems. The viscosity distribution along the directionnormal to solid surface is approached by a function proposed in this paper. Based on theformula, lubricating problem of thin film lubrication (TFL) in isothermal and incompressiblecondition is solved and the outcome is compared to the experimental data. In thin filmlubrication, according to the computation outcomes, the lubrication film thickness is muchgreater than that in elastohydrodynamic lubrication (EHL). When the velocity is adequatelylow (i.e., film thickness is thin enough), the pressure distribution in the contactarea is close to Hertzian distribution in which the second ridge of pressure is not obviousenough. The film shape demonstrates the earlobe-like form in thin film lubrication, whichis similar to EHL while the film is comparatively thicker. The transformation relationshipsbetween film thickness and loads, velocities or atmosphere viscosity in thin film lubricationdiffer from those in EHL so that the transition from thin film lubrication to EHL canbe clearly seen.