Abstract: Objective: To study the inhibitiory effect of cordycepin on macrophage hyperactivation induced by lipopolysaccharide ( LPS) .Methods: Mouse RAW264.7 macrophages were cultured with LPS ( 1 μg/m L) and different concentrations of cordycepin ( 0.1~10 μmol/L) .The cell viability was evaluated by MTT assay.Nitrite levels in culture supernatant fluids were examined by Griess assay. The release of cytokines ( TNF-α, IL-1β, and IL-6) was examined by enzyme-linked immunosorbent assay ( ELISA) .The cytosolic free Ca2 +level ( Ca²⁺i) of macrophages was measured by staining the cells with Fluo-3/AM followed by flow cytometry analysis.The scavenging activity of cordycepin against hydroxy radical (·OH) , peroxynitrite ( ONOO-) , and superoxide anion ( O₂^-·) was examined by salicylic acid, L-tyrosine, and pyrogallic acid methods, respectively. Results:Cordycepin ( 0.1~10 μmol/L) could inhibit the release of NO and cytokines ( TNF-α, IL-1β, and IL-6) without the influence of cell viability in LPS-activated macrophages. Cordycepin ( 10 μmol/L) could suppress theCa²⁺ilevel in LPS-activated macrophages. In addition, cordycepin showed direct scavenging activity towards ·OH, ONOO-, and O₂^-· free radicals, significantly.Conclusion: It is suggested that cordycepin can inhibit LPS-induced release of NO and cytokines ( TNF-α, IL-1β, and IL-6) by suppressing theCa²⁺ilevel and directly scavenging ·OH, ONOO-, and O₂^-· free radicals. Cordycepin may have therapeutic potential in the treatment of inflammation-related diseases accompanied by macrophage activation.