In recent years, plasma sterilization is studied as a low temperature and a safe new sterilization processing method compared to the conventional sterilization method. This research investigated the sterilization performance using He - N2 - O2 mixture gas flowing microwave plasma excited at 2.45 GHz. This sterilization process in this experiment can be completed in a short time using the synergistic effect of oxygen radical and UV photons produced by plasma. In this experiment, Geobacillus stearothermophilus ATCC 7953 was able to be completely sterilized in 10 minutes.