Abstract: The geometrical and mathematical models of angular contact ball bearing are established,through solving the Reynolds equation considering thermal and time-varying effects,the transient thermal mixed lubrication analysis in the process of start-up and shut-down with different acceleration about ball bearing is analyzed. The transient thermal mixed lubrication status under different acceleration in the start-up process is considered. Results show that the bearing enters elasto-hydrodynamic lubrication form as the increasing of rotate speed. The moment that enters elastohydrodynamic lubrication form is delayed as the increasing of slip-roll ratio,the film thickness gets thinner in the condition of the same rotate speed. The film temperature rises as the increasing rotate speed and turns to elevate slowly. The increasing of bearing acceleration can bring forward the phase from boundary lubrication form to elasto-hydrodynamic lubrication form and the larger of the acceleration the higher of the film temperature. The film thickness of the bearing during shut-down process is thicker than the film thickness during bearing start-up process due to the squeeze film effects. As the different lubrication performance of ball bearing,temperature during bearing shut-down process is lower than that during bearing start-up process.