Abstract: A new mathematical model on the condition of thin film lubrication is established by taking into account the effect of electric double layer.In the present paper,experiments are carried out on a self-made tester.With a composite block and a sliding disk,influence of electric double layer on thin film lubrication is studied.Two different methods are used to reconstruct the field of electric double layer so as to change the effect of electric double layer.One is to change ionic concentration of lubricants by adding additives,and the other is to apply an external electric field on friction pair.According to theoretical analysis,both methods will apparently change electro-viscosity of the lubricant film so as to change the lubrication performances.After theoretical calculation of electro-viscosity is amended according to the experimental results,the equations of electro-viscosity are presented.The results show that equivalent viscosity of fluid induced by the effect of electric double layer apparently increases with decrease of thickness of the film while lubrication film is thin enough.Effect of electro-viscosity is weakened as thickness of the film increases.Moreover,effect of electro-viscosity increases with increase of external electric field at first.When value of voltage reaches a certain value,electro-viscosity begins to decrease.