Abstract: To study the lubrication states of the roller enveloping hourglass worm drive, the isothermal line contact minimum film thickness is established based on the research of meshing theory of the roller enveloping hourglass worm drive and the theory of elastohydrodynamic lubrication(EHL). Based on this, a calculation model of the lubrication state of the roller enveloping hourglass worm drive is established, the distribution of the film thickness ratio is analyzed. The influence that orifice coefficient, roller radius, center distanceon, lubricant dynamic viscosity to lubrication characteristics of this worm drive are analyzed at last. It can be concluded as that the roller enveloping hourglass worm drive is dominated by the partial EHL in the working cycle. The example analysis results indicated that the EHL states can be effectively improved by properly increasing orifice coefficient, center distanceon, lubricant dynamic viscosity and reduce the roller radius.