Abstract: Structural aseismic characteristics can be explained more clearly by dynamic analysis based on energy concept. The concept of structural aseismic design and research information is introduced firstly. From seismic elastic and inelastic time history analysis of lumped mass MDOF structure systems, the storey energy distributions are analyzed in this paper. Energy concentration and its causes are pointed out. Based on the analysis of results, this paper gives the rule of ECS and suggests a method for calculating inelastic displacement of ECS relying on equal cyclic energy criteria of vibration.