The EMC standard of frequency range of 150KHz-30MHz on restraining the conducted CM EMI are becoming more serious in the application. CM inductance & filter capacitor were used to restrain the CM EMI. Ferrite core or common Nanocrystalline core are popular in domestic market as common mode choke cores, but high high-frequency volume and impedance reduction from 150KHz to 30MHz due to the operating frequency limitation makes these cores unworkable. In this case , we developed advanced higher property Nano-crystalline common mode choke cores as solution for EMC common mode choke cores requirement, and were applied to the EMC of switch power modules, UPS power supply, communication power supply, inverter, transducer, home appliance.