At present, Electro Magnetic Compatibility(EMC) design has become an important part of the design of complex systems. There are three main methods of EMC design: test analysis method, empirical analysis method and modeling simulation method. Aiming for the increasingly complex electromagnetic environment requirements, combined with practical difficulties in EMC design of complex systems with high integration and the specific circumstances of EMC designers, the feasibility of the three EMC design methods is analyzed, and the scope and problems of the three methods are pointed out. From a practical point of view, a proposal to establish an EMC database for EMC test data, EMC design experience and electromagnetic compatibility model is proposed. It is of practical significance to improve the electromagnetic compatibility of complex systems.