Natural phenanthrene derivatives are considered to be important resource for the anti-inflammatory therapeutics, but their structure-activity relationship and mechanisms are still unknown. In this study we evaluated 20 synthesized phenanthrene analogs in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Compounds 10, 11 and 17 were found to inhibit the production of nitric oxide (NO) with IC50 values of 37.26μM, 5.05μM and 20.31μM, respectively. Compound 11 decreased LPS-induced expression of inducible NO synthase (iNOS), inhibited phosphorylation of p38 mitogen-activated protein kinase (MAPK) and serine/threonine kinase Akt. It also suppressed the phosphorylation and degradation of inhibitory kappa B-α (IκBα). Data obtained suggest that compound 11 exerts anti-inflammatory effects by inhibiting p38 MAPK and nuclear factor κB (NF-κB) pathways, which warrants further investigation as a new anti-inflammatory pharmaceutical tool.