Abstract: A model has been established to show the effect of elastic plastic asperity deformation on the factor of flow in partial hydrodynamic lubrication (PHL) on the basis of an elliptic elastic plastic asperity microcontact model. Some examples are calculated using this model. The results show that the larger the elastic plastic deformation,the greater the influence on partial lubrication. The influence of elastic plastic asperity deformation on partial hydrodynamic lubrication (PHL) is largely dependent on the comprehensive properties of the surfaces and the degree of elastic and plastic deformation.