BJ493ZLQ4A diesel engine is based on the primary model of BJ493ZLQ3,the exhaust level is upgraded to National GB5 through improving the design of combustion and injection systems.Significant changes have occurred in the diesel lubrication system,so it need to analyze and calculate the lubrication system properties.According to the structures,technical parameters and indexes of the lubrication system,the lubrication system model of BJ493ZLQ4A diesel engine was established with Flowmaster.The properties of the diesel engine lubrication system,such as the oil flow rate and pressure at different speed were analyzed according to the schemes of choosing big or small oil filters.The calculated values of the main oil channel pressure are in good agreement with the experimental results,which verify the correctness of the proposed model.The calculation results show that the values of main oil channel pressure and maximum oil flow rate for the scheme of choosing big oil filter are satisfied with the requirements of design.