Two toxin polypeptides (designated RSAPⅠ and RSAPⅡ) have been isolated from Sea anemone Actinia cari. Toxins isolation was accomplished by freezing-thawing extraction, acetone fractional precipitation, cation exchange chromagraphy on SP Sephadex C 25 and reverse phase HPLC on ODS C₁₈.They were found to be homogenous by SDS-PAGE and MALDI-TOF-MS, and their relative molecular masses are 5 008 and 4 992, respectively. They are found to be active on sodium channel in Guinea pig cardiac cell, RSAPI, increasing inward Na(+) currents, opens the sodium channel; RSAPⅡ, decreasing inward Na(+) currents, inhibits the opening of the sodium channel. The circular dichroic spectra of these two polypeptides are 100% β turn.