In this paper, we present a EMC model of a DC-DC converter based on ICEM(Integrated Circuit Emission Model) methodology. The suggested DC-DC converter uses 9MHz switching frequency at 90MHz operating frequency obtained from clock frequency of 180MHz. Simulations for conducted emission(1Ω/15Ω Method) and radiated emission(Near Field Scanning) are performed according to EMC(Electromagnetic Compatibility) standards of IEC61967. In simulated results of conducted and radiated emission, the largest EM noise peak occurs in an oscillation frequency where power dissipation is lower than that for other frequencies. To analyze this unexpected Em noise, EM noise simulation using ICEM methodology must be performed in an early design stage of IC.