A new approach for fault information analysis of relay protection based on expert system is proposed. It adopts the protection startup numbers of the single protection device as the criterion of identifying the grid fault, which is simple and has strong adaptability. The level of voltage sag is used to search for the kernel fault recorder documents, which realizes the automatic identification of the fault recorder documents. The recursive strategy for fault synthetic analysis of grid relay protection is applied to gain the evaluation results, which ensures the rapidity and completeness of this method. The application results in Anhui electric power relay protection and fault information system show its effectiveness. The algorithm as a fault synthetic analysis tool can be applied to a wide range of engineering domains.