In view of the influence of boundary film on lubrication state of friction pairs,a model of boundary film strength which can comprehensively reflect the comprehensive influence of pressure and shear rate on the failure of boundary film was proposed,and the model parameters were obtained by fitting the test results of lubrication state.Coupling the boundary film strength model with hydrodynamic lubrication model and rough surface contact model,a mixed lubrication model considering the boundary film strength was established.The simulation results were verified by the lubrication test results of the bearing shell friction tester.Compared with the existing typical mixed lubrication models,the proposed mixed lubrication model can more accurately reflect the actual lubrication state of friction pairs and the variation rule of friction coefficient.The mixed lubrication model considering boundary film strength was applied to analyze the lubrication state transformation characteristics and mechanisms of the bearing shell.The results show that under the mixed lubrication state where boundary lubrication exists,when the load is less than the ultimate load,the boundary film hardly breaks down,and the friction coefficient increases slowly with the increase of load,and all of its values are small.When the load exceeds the ultimate load,the boundary film breaks down,dry friction occurs in the asperitiy contact area of the friction pair,and the friction coefficient increases suddenly,indicating that the friction pair transitions from a mixed lubrication state dominated by boundary lubrication to a lubrication state dominated by dry friction.