Taking globoidal indexing cam mechanism as the research object,the lubrication state and elastohydrodynamic lubrication film thickness of globoidal indexing cam mechanism during indexing period meshing were studied.The mathematical model of the mechanism was established by using the conjugate principle of spatial envelope and the method of rotating variable.According to the Hamrock Dowson formula of minimum oil film,it was concluded that the entrainment speed,induced principal curvature and contact stress were the main factors influencing the formation of lubricating oil film thickness under steady state condition.Based on the principle of spatial conjugate,a new algorithm of contact stress was proposed and verified.The contact stress,oil film thickness and film thickness ratio of the mechanism at different speeds were simulated.The results show that it is very difficult to form elastohydrodynamic oil film in the meshing in and meshing out sections during the low speed transmission of the mechanism,which provides a theoretical basis for optimizing the lubrication performance of the mechanism.