For the lubrication of rolling bearing,the influence of bearing surface roughness and solid particles on lubricating oil can not be ignored,so it is necessary to modify the Dowson-Higginson(D-H) equation.Considering the coupling effects of surface roughness,solid particles,bearing dynamics and multi-scale parameters of roller modification,the numerical solution of complex lubrication model of cylindrical roller was established and solved,and an improved formula of minimum film thickness based on D-H formula was proposed.By using bearing dynamics to solve the actual load and velocity of roller,combining with finite length rolling bullet flow lubrication and considering surface roughness and micropole fluid effect,a finite length elastohydrodynamic lubrication model was established,and an improved oil film thickness equation was derived.The results show that there is “end face effect” in the lubrication of cylindrical roller bearings,the minimum oil film thickness and the maximum oil film pressure appear at both ends of the roller,and this phenomenon can be improved by the design of roller convexity.The results of numerical examples show that the improved film thickness equation has higher accuracy.This equation accurately and comprehensively describes the actual lubrication condition of cylindrical roller,and can provide theoretical and analytical tools for its structural design,processing method,transmission efficiency,lubrication characteristics,fatigue life and reliability research.