This paper proposes a fault detection method based on the residual evaluation strategy. On the basis of the system residual error data only, do not rely on the system analytical model for fault detection, a new theoretical basis is provided for fault detection based on the data-driven method for the complex system. In order to improve the accuracy of the system fault detection, the fault detection threshold is optimally designed on the basis of fault miss alarm ratio and false alarm ratio. And by detecting the possible failure of the excitation system in the vehicle power system, the accuracy and effectiveness of the proposed method is verified.