Partial lubrication in cold rolling process has been investigated. The average flow Reynolds equation for rolling lubrication is set. This equation considers the pressure-viscosity effect and the average flow effect. Lubricating factors such as inlet velocity, surface waviness, lubricant viscosity are studied in analyses. The results for lubrication equation show that inlet velocity and lubricant viscosity have some influence on the value of rolling friction. And the results also show that surface waviness has great influence on both rolling pressure and rolling friction.