In this study, it was examined the effects of the pre-treatment of gamma radiation on composting and pathogen bacteria reduction. It was expected that the strong oxidants would be produced by irradiation and they made a critical role in destructing and/or enfeebling solid materials. For the start-up of the all composting reactor, a feedstock was prepared by pig manure and sawdust material mixed of the C/N rate 25. AII reactors were packaged with the 4.5kg feedstock. They were irradiated by a cobalt-60 gamma irradiator at the dose of 0, 3, 5, 10 and 20 kGy. The temperature pattems of composting reactor were not different between irradiated and non-irradiated reactors. The CO2 gases of the irradiated reactors were decreased than non-irradiated reactor, the optimal composling condilion was 10kGy irradiation and 10~20% seeding ratio.