In current lubrication analysis of journal bearing,the oil film is usually supposed to only have positive pressure zone.In fact,the negative pressure zone is always exist in the oil film of the whole journal bearing.Based on the massconserving boundary condition and the modified Elrod’s algorithm,the governing equations that can automatically determine the dynamic boundary and the unified lubrication equation for complete oil film zone and cavitation zone were obtained.The lubrication performance of journal bearing under different conditions was simulated numerically,and the impact of the cavitation effect on the lubrication performance of journal bearing was analyzed.The results show that the zone and distribution of the bearing oil film pressure is different from that under the Reynolds boundary condition in the same working condition when the cavitation effect is taken into account.In different working conditions,the cavitation effect has different effect on the distribution of oil film pressure and the lubrication performance of the journal bearing,such as the side flowrate of bearing changes obviously and the friction power loss increases a little.Thus,the cavitation effect on the lubrication performance of journal bearing is not always favorable.Therefore,it is necessary to consider the effects of cavitation in different working conditions on the lubrication performance of journal bearing in the design of journal bearing.