In order to solve the problem of reliability sensitivity analysis of tracked vehicle transmission gears in the presence of different failure modes, the random perturbation theory, the fourth moment method and Edgeworth series are employed to calculate the statistical correlation and reliability index of each performance function of the failure modes, and the reliability of the failure modes of the mechanical component with the arbitrary random distribution parameters. According to the future that only a few potential failure modes existed in the component and the overall fails when a failure mode occurs in parts, the failure of the component is regarded as the failure of a series system. On this basis, the calculating formulas of reliability sensitivity of the mean and variance of random variables are derived with the gradient method. The example illustrates that this method could effectively estimate the reliability sensitivity of mechanical components with multiple failure modes and provide reference for the optimization design of mechanical components.