Lubrication situation of the tappet assembly of an electronic unit pump was analyzed.According to the defect of low mass flow rate and asymmetric distribution of lubricating oil in current structure of lubrication,the configuration of the tappet assembly was improved by adding inlet orifice and drain hole.The simulation result shows that the improved lubrication structure significantly increases the oil flow rate in the annular gap of the tappet assembly and between the rollercam pairs,which makes the distribution of the oil in the tappet assembly more reasonable.Full speed and full load reliability test results of 100 h validates that the lubrication effect of the tappet assembly is improved,and the reliability of the electronic unit pump system is improved obviously.