It is believed that there are many accelerators of the ozonolysis of diene rubber, but the influence of these accelerators has not been examined in detail. We investigated the influence of humidity on the ozonolysis of diene rubber by observing ozone cracks on a rubber surface and analyzing the surface of the ozonoly sis rubber by PT IR after ozone treatment. The results indicated that humidity accelerates the formation of cracks and oxidation on the rubber surface. ESR (Electron Spin Resonance) was able to detect carbon radicals transferred from hydroxyl radicals because of ozone and humidity. The radical reaction occurred in high humidity with ozonolysis, but not in low humidity.