As a key component of the auto-brake system, the automatic brake adjuster is related to the safety of vehicle driving. The possibility of failure of the automatic brake adjuster is analyzed by fatigue test. The results show that the rectangular compression spring and the helical compression spring are the key factors affecting the failure of the automatic brake adjuster. By using MATLAB, it can be seen that the fatigue life of the automatic brake adjuster obeys the Weibull distribution of three parameters, combining with competitive fault model to analyze the reliability of the automatic brake adjusters. Based on the model, the least squares method and the maximum correlation coefficient method are used to analyze the reliability of the automatic brake adjuster. The life data in the experiment were used to estimate the parameters. The example shows that the method is simple, convenient and practical, and the Weibull distribution of the competitive fault model can accurately reflect the statistical properties of the data of the automatic brake adjuster fatigue test, which is of good engineering application value.