In order to test the reliability of automobile hydraulic, the vibration reliability test needs to be done. The fixture, which is used to clamp and fix the hydraulic system, is one of the most important components of the test. So the dynamic performance of the fixture has great influence on the vibration test. According to the figure and setting localization of electronics, the three-dimensional model of fixture was constituted. The modal frequency and vibration modal were calculated using FEM. By the result of analysis, the structure of the fixture was mended to meet the test requirement.