It is urgent to solve various problems in electromagnetic (EM) engineering under the increasingly complicated environment. Some expert systems (ES) come into being just to keep up with the demand for solving these problems. Combined with the analysis of development of ES technology and the development trend of EM engineering software in recent years, the application of ES technology in EM engineering is discussed, and especially the progress of complete ES in electromagnetic compatible (EMC) is introduced. It is urgent to solve various problems in electromagnetic (EM) engineering under the increasingly complicated environment. Some expert systems (ES) come into being just to keep up with the demand for solving these problems. Combined with the analysis of development of ES technology and the development trend of EM engineering software in recent years, the application of ES technology in EM engineering is discussed, and especially the progress of complete ES in electromagnetic compatible (EMC) is introduced.