Emission spectrum analysis method was used for the lubricating oil analysis of MTU396 type of diesel engine,and the distribution rules of wear elements concentration were analyzed.The wear elements concentration monitoring threshold values of propelling engine and generating electricity engine were calculated through three line value method and maximum entropy method,and were compared with the actual monitoring results.Results show that the traditional three line value method is more suitable for the emission spectrum wear elements threshold calculation of MTU396 diesel oil in abundant samples cases,and the calculation results more accord with actual monitoring data.When the MTU396 diesel engine are used as propelling engine or generating electricity diesel engine,the oil emission spectrum wear elements concentration monitoring threshold values are different,the threshold values should be set separately according to their working conditions.