Abstract: As an important penalty used by EC Commission in Cartel cases, Fining policy is developed quickly in past years and established its own operation system especially during the modernization of EC Competition Law in 2004. The present fine policy system further increases the clearness and transparence of the specific criteria of fine, clarifies the conditions and procedure, strengthens the determinacy and anticipation of fine policy thereby boosting its deterrent effect. Coupled with some other methods for immunity or a reduced fine, fine policy constitute the most efficient weapon in the Commission's armory to fight Cartels.