OB JECTIVE To study the anti-inflammatory effect of couplet medicinals of Achyranthes bidentata -Eucommia ulmoides. METHODS Mouse macrophage RAW 264.7 were divided into blank group ，model group ，A. bidentata group（800 μg/mL），E. ulmoides group（800 μg/mL）and low- ，medium- and high- concentration groups of couplet medicinals of A. bidentata - E. ulmoides （400，800，1 600 μg/mL）. Excep for blank group and model group ，the other groups were added with corresponding drugs for 6 hours；then blank group was continued to add into the medium ，while model group was added into 10 μg/mL lipopolysaccharide （to induce the inflammatory model ）；other groups were added into corresponding drugs and 10 μ g/mL lipopolysaccharide. The levels of inflammatory factors [nitric oxide （NO），interleukin-1β（IL-1β），IL-6，tumor necrosis factor-α （TNF-α）] were detected ，and Jin ’s formula was used to evaluate the effects of A. bidentata -E. ulmoides . The expression of inducible nitric oxide synthase （iNOS），cyclooxygenase-2（COX-2），nuclear factor kappa-B （NF-κB）and inhibitor α of NF-κB （IκBα）as well as the phosphorylation of NF-κB p65，IκB kinase（IKK），p38 mitogen-activated protein kinase （p38 MAPK）， extracellular signal-regulated kinase （ERK）and c-Jun N-terminal kinase （JNK）were determined. RESULTS Compared with blank group，the level of inflammatory factors ，protein expression of iNOS and COX- 2 as well as the phosphorylation of NF-κB p65， IKK，p38 MAPK，ERK and JNK were increased significantly （P＜0.01），while the protein expression of IκBα was decreased significantly（P＜0.01）. After intervention of couplet medicinals of A. bidentata -E. ulmoides ，the level of inflammatory factors ，the expression or phosphorylation of above proteins were reversed significantly （P＜0.05 or P＜0.01），and couplet medicinals of A. bidentata-E. ulmoides had a synergistic effect. CONCLUSIONS The couplet medicinals of A. bidentata -E. ulmoides have synergistic anti-inflammatory effect on RAW 264.7 cells. Its mechanism may be related to the inhibition of NF-κB/MAPK signaling pathway related protein expression.