Objective To investigate the effect of cysteine protease inhibitor of snake venom (sv-cystatin) on invasiveness and metastasis of melanoma cells. Methods The recombinant plasmid pcDNA3.1/sv-cystatin was constructed and transferred into mouse melanoma cell line B16F1 by lipofection technology. The positive clones were screened by G418 and the sv-cystatin expression was detected by RT-PCR and Western blotting. The ability of tumor cell invasion was identified by Boyden chamber in vitro and tumor invasion animal model in vivo. The ability of tumor cell proliferation and adhension was also determined by MTT assay. Results Expression of svcystatin was detected in B16F1/sv-cys cells after genetransfection. Transfection of svcystatin significantly decreased the invasion and migration of B16F1/sv-cys cells along with obviously inhibited the experimental pulmonary metastasis in vivo, but the proliferation and adhension capacity of B16F1/sv-cys cells had no change.Conclusion Transfection of sv-cystatin gene into mouse melanoma cell line results in the suppression of