Electret filter is good enough to protect health and environment from air pollution. The reason why is gathering particles not only by mechanical mechanism but also by electrostatic attraction. Especially this filter is shown lower pressure drop than general mechanical filters as glass fiber. For making electret filter media using polypropylene meltblown(M/B) nonwoven, the nonwoven is charged with corona which was supplied high voltage DC, AC, and pulse with DC power. The electret filter media is tested with $0.3{mu}m$ sodium chloride and dioctyl phthalate(DOP) aerosol. Results revealed that filtration performance of electret filter media increased as corona was applied with higher voltage and with AC power rather than DC, and fiber diameter was fine and uniform.