Objective: This study investigated the anti-inflammatory function of superoxide dismutase by investigating the free radicals produced in hamster oral mucosa induced by paraquat. The efficacy of superoxide dismutase scavenging oxygen free radicals was also analyzed. Method: Electron spin resonance spectroscopy, a direct technique, was used to measure the free radicals present in the inflamed mucosa. Results: The results showed that the spectra of the inflammatory tissues exhibited three different signals with different power saturation. Among these signals, signal b was mostly like that of oxygen free radicals. The realtive OFR intensity was significantly reduced by SOD (P < 0.05). The ability of scavenging OFR in the superoxide dismutase group was over 66 times that of the control group. Conclusion: Superoxide dismutase scavenging oxygen free radicals may play an important role in protecting against inflammation in oral mucosa.