Objectives : The purpose of this study was to investigate the anti-inflammatory effects of the aqueous extract of the steamed radix of Rehmanniae glutinosa (SRG) on periodontitis in ligature-induced rat model. Methods: To induce the periodontitis, ligature was placed around the lower first molar in rats. Rats were divided into 4 groups (n = 7), NL (non-ligatured and vehicle-treated), L (ligatured and vehicle-treated), SRG1 (ligatured and 1 mg/kg SRG-treated) and SRG100 (ligatured and 100 mg/kg SRG-treated). Vehicle or SRG solution was applied daily for 14 days and then all experimental rats were sacrificed. To examine the effect of SRG solution on periodontitis, the level of alveolar bone loss, cementum regeneration, gingival tissue degradation, and osteoclast cell numbers were analyzed. Results: Alveolar bone loss was inhibited in ligature-induced periodontitis rats treated with SRG treatment. Histopathological cementum was recovered in SRG1 and SRG100 groups. SRG extract inhibited gingival tissue degradation induced by ligature. In addition, the numbers of osteoclast cells were decreased by treatment SRG in periodontitis rats. Conclusion: Taken together, these results suggest that SRG have inhibitory effects against periodontitis. Therefore, the steamed radix of Rehmanniae glutinosa has may be a potential alternative for periodontitis.