A halophilic V. vulnificus is an estuarine microorganism that has been associated with fatal wound infection and life-threatening septicemia. Hemolysin is defined as toxic substance produced by various species of bacteria including V. vulnificus. Hemolysin from marine V. vulniiicus was purified and the effect of pH, temperature, metal ion on the activity of hemolysin, and thermostability of hemolysin were tested in this study. Hemolysin lysed the sheep red blood cell and the optimum pH was 8.0, the optimum temperature was 40℃, and K^+ increased but Mn^2+ decreased the hemolytic activity of hemolysin, but hemolysin was unstable to heat.