Electromagnetic radiated emission of power bus structure has been investigated. Transient current flows at the power supply terminal was assumed to an exciting source, and the power bus consisted of power and ground planes was assumed to work as antenna of common mode radiation. Two simulation approaches were studied; One is a time-domain response-based approach, and another one was a frequency response-based approach. The test board consisted of 4 conductive layers was fabricated to verify simulation results. Then, transient power supply current of the IC was monitored, and far-field radiated emission was measured in an anechoic room. The simulation results obtained by both approaches showed a good agreement with the measurement results.