In order to determine the main cause of the failure of the lubrication pump of the machine tool, the traditional fault tree analysis method is applied to the fault analysis of the machine lubrication pump by combining the gray correlation analysis method with the traditional fault tree method. Through the structural importance of the fault tree bottom event, the gray correlation degree of each bottom event of the machine lubrication pump was obtained, and the possibility of occurrence of various failure modes could be accurately determined. The result shows that the control panel failure is the most common failure of the lubrication system. The main reason is that this is consistent with the actual test results. This method can provide a new idea for the improvement of machine tool lubrication system, fault diagnosis and reliability improvement, and provide reference for state prediction.