Abstract: The ability of Bdellovibrio strain HD94-12-7 in the lysis of host bacteria,Vibrio fluvialis Biovar Ⅲ strain WY91-24-3 under various culture conditions was studied.In the autoclaved distilled water, autoclaved pond water, autoclaved tapwater and Tris buffer, the parasitic bacteria appeared to have good lytic activities in reducing the number of the host bacteria.The temperature ranging between 20 and 35℃was more conducive to Bdellovibrio attack than the temperature less than 15℃;At pH6.5, 6.8, 7.2, 7.7, 8.1 the Bdellovibrio was most effective for red ing the number of Vibrio fluvialis Biovar Ⅲ strain WY91-24-3, while pH values less than 5.6, or greater than 8.6, the surviving of Bdellovibrios was influenced.Ions of Ca++,Mg++ apparently enhanced the lytic ability of Bdellovibrios.The present study demonstrated that Bdellovibrios effectively reduce the level of Vibrio fluvilalis Biovar Ⅲ strain WY91-24-3 under experimental conditions.