The purpose of this study was to investigate the effects of Polygonum multiflorum Water Extract (PMWE) on the production of inflammatory mediators in RAW 264.7 mouse macrophages induced by Lipopolysaccharide (LPS). We examined effect of PMWE on the cell viability of RAW 264.7 macrophages cells and investigated anti-inflammatory effect of PMWE by the production of proinflammatory cytokines such as Nitric Oxide (NO). No significant changes have been found in the mouse macrophage cell viability by the PMWE at the concentration of 0.1, 0.5 and 1 mg/ml. Furthermore, PMWE significantly inhibited the production of NO in the LPS-induced macrophages at the concentration of 0.1, 0.5 and 1 mg/ml. In addition, The PMWE inhibited the production of NO more strongly than 2, 3, 5, 4’-Tetrahydroxystilbene-2-O-β-D-Glucoside (THSG), which is well-known as a strong antioxidant agent. These results suggest that PMWE has anti-inflammatory effect through the regulating the production of NO in the LPS-induced macrophages.