Aimed at the failure of abnormal heat generation in a ships stern tube,the fault background of the ship was analyzed.Through the physical and chemical index analysis,spectral element analysis,infrared spectrum analysis,and ferrography abrasive analysis of the new oil and used oil samples of the ships stern tube,it is found that the lubricating oil of the stern tube is mixed with other oil,and the bearing of the stern tube is seriously worn.According to the calculation results of the minimum oil film thickness formula,it is found that the size of the wear particles greatly exceeds the thickness of the lubricating oil film of the stern tube,resulting in the sharp wear of the stern tube.The comprehensive analysis shows that the mixed oil causes the poor performance of the lubricating oil,resulting in the serious wear of the bearing bush,which is the main cause of the abnormal heating of the bearing bush.