The more simple and precise method were developed based on the several references which are relative to the biofilm measurement and applied for measuring a biofilm thickness built on media operating in the wastewater treatment reactor, and proved to be higher accuracy, quickness and easiness than other methods. The media were electrified with low voltage of electricity for increasing microorganism activity and for controlling the biofilm thickness on media. As shown in the results, the biofilm thickness on the electrified media was almost constant and thinner than that on the normal media regardless of the quality of media surface. The bioflim thickness on normal media, however, was confirmed to be higher than that on the electrified media and was highly influenced by surface quality. By which, the electrified media was proved to be very efficient for controlling biofilm thickness and activity.