Abstract: Objective To study the mechanism of action between matrix metalloproteinase-3（MMP-3） and tumor necrosis factor-alpha（TNF-a） in ankylosing spondylitis（AS） patients. Methods After peripheral blood mononuclear cells（PBMC） were isolated from 5 AS patients and synovial fluid mononuclear cells（SFMC） were isolated from 6 AS patients with synovial fluids in their knee joints,the PBMC and SFMC were stimulated in vitro with human recombinant MMP-3 and changes in TNF-α expression were detected by enzyme linked immunosorbent assay（ELISA）.（Adherent cells were also isolated from PBMC of 7 patients with spondyloarthropathy（SpA） using（human recombinant MMP-3） stimulated adherent cells in vitro and the concentration of TNF-α was determined by ELISA）. Results Different concentrations of human recombinant MMP-3 induced release of TNF-α by stimulating PBMC in vitro in a dose-dependent manner. The SFMC of AS patients could automatically produce TNF-α even though it was not stimulated by human recombinant MMP-3. Conclusion Interaction between MMP-3 and TNF-α may play an important role in the pathogenesis of AS. MMP-3 may also selectively stimulate monocytes or macrophages rather than lymphocytes.