Halotolerant protease produced by Halomonas marisflava KCCM 10457 was partially purified through ammonium sulfate precipitation and Sephacryl S-200HR gel permeation chromatography. Optimal pH and temperature of protease were 11.0 and $45^{circ}C$, respectively. Enzyme activity was inhibited by $Cu^{2+}$, $Hg^{2+}$, $Fe^{2+}$, and $Fe^{3+}$, and selectively inhibited by p-chloromercuribenzoic acid (PCMB), suggesting this enzyme is cysteine protease. The enzyme is halotolerant, because it retained 77% of original activity in presence of 3.33 M NaCl. The protease showed broad substrate specificity to various natural proteins; BSA, casein, egg albumin, gelatin, and hemoglobin.