There are friction problem such as surface roughness peak contact in water lubricated bearings,and a appropriate length diameter ratio can improve the lubrication state of bearings.Taking heavyload water lubricated bearings as the research object,a thermal mixed lubrication model of water lubricated bearing was established.By solving the model with finite differential method,the effect of length diameter ratio on the lubrication performance of heavyload water lubricated bearings was studied.The results show that under constant load conditions,increasing length diameter ratio can improve capacity of water film,increase the minimum film thickness and improve the bearing lubrication state,and can make the bearing pressure distribution uniform to decrease the effect of stress concentration and improve the life of bearing.At low speed,increasing length diameter ratio can decrease the friction coefficient,but the tendency is opposite at high speed.A high length diameter ratio can decrease the bearing temperature but will hinder the discharge of water.