This paper simulated discharge progress and partial discharge using needle-plan electrode system in air, in this time with discharge progress, studied the distribution of frequency spectrum of the radiated electromagnetic waves using biconical antenna and spectrum analyzer. From results of this study, a method was introduced for measurement and analyzation of the radiated electromagnetic waves in accordance with AC discharge progress in air, Besides, according to the consideration of the mutual relation between frequency spectrum of the radiated electromagnetic waves and discharge progress, it was confirmed that detecting partial discharge and estimating discharge progress were possible.