Pathogenic bacteria such as Cryptosporidium pan씨m has become an increasing concern due to public health. Cryptosporidium paroum ωas currently considered the microbial water contaminants of the most resistant to disinfection by chemical disinfectants. In contrast, disinfection methods using ozone and gamma ray were considered effective due to a high disinfection for Pathogenic bacteria without formation of undesired halogenated by-products. This study was performed to investigate the disinfection on Bacillus subtilis spores by ozone and gamma ray. As the results of the experiment, Bacillus subtilis spores almost were not detected at the condition of 120 min exposure by ozone and gamma dose of 2kGy. Besides, regrowth potential of Bacillus subtilis spores after Ozone and gamma ray were monitored during 4 days. Regrowth of Bacillus subtilis spores after ozone 120min ap야ared after 3days, and the maximum regrowth of bacillus subtilis spore was 30%. However, disinfection efficiency on Bacillus subtilis spore after gamma ray dose of 1kGy approached 98% and regrowth was hardly observed for 4 days. Therefore, it can was suggested that disinfection by gamma ray proved to be the most effective disinfection method since gamma ray prevent regrowth in disinfected drink water.