This paper deals with the design criteria and conduction noise reduction of electronic ballast system which is based on half-bridge series inverters. The system is theoretically analyzed in six modes and operating frequency range is selected to obtain the high efficacy and no sound noise. It is proposed the criteria for determining the values of L and C which are the dey points in system design Because of high operating frequency, electromagnetic noise, especially conduction noise, is a serious problem in electronic ballasts. To reduce the conduction noise, the operation and attenuation characteristics of noise filter are analyzed and the method to determine the values of filter elements is proposed. Also, the parasitic components of the inductor and capacitor are taken into consideration in filter analysis. Digital simulations and experiments are carried out to prove the theoretical results. And perfor mances of the system are verified through tests.