Abstract： Objective To investigate the inhibitory effect and antitumor mechanism of recombinant protein of buthus martensii venom on A549 human lung adenocarcinoma cell line.Methods The inhibitionof proliferation in vitro was measured by methyl thiazolyl tetrazolium (MTT)assay.Influence of [ Ca2+]i by recombinant protein of buthus martensii venom was observed by fluorescence microscope and flow cytometry.And then to explore the source of Ca2+ when[Ca2+]i was aherating.Results The protein could inhibit A549cell proliferation.Fluorescent microscope assay showed enhanced fluorescent intensity after 48 hours,and itmeaned the increasing[Ca2+]i concentration.Flow cytometry assays showed the recombinant protein can significantly increase the concentration of[ca2+]i in tumor cells under different circumstances(P<0.05).Conclusion The recombinant protein can obviously inhibit the proliferation of A549 cell line,and itsmechanism has relationship with tumor cell apoptosis through increasing[Ca+]i level of tumor cell asresulted by openning the calcium ion channel on the membrane and releasing calcium ion in tumor cells.