One of the main differences between digital substation and conventional substation is the application of electronic transformer. In the substation electromagnetic environment， the occasional output abnormal data of electronic transformer will lead to incorrect behaviors of protections， and reduce the reliability of power supply. According to the characteristics for the abnormal data of electronic current transformer， an abnormal data resisting method based on sampling data amplitude comparison is proposed. The simulation results and practical engineering applications show that the proposed method has high reliability without influencing the action speed of protection.