Bdellovibrio can lyse pathogenic bacteria and clean up waters. 4 strains of Bdellovibrio sp., designated Bh04-4, Bh04-41a, Bh04-A + and Bh04-1f, were isolated from seawaters used Bh04 as host bacterium. After confirmation to be Bdellovibrio sp. by electron microscopy and specific PCR method, their growth conditions and lytic ability on 61 bacteria from various sources were performed. Results showed that all four Bdellovibrio grew in salinity in the range of between 1% and 3%, with 3% salinity being the most suitable one. They grew in the range of temperature from 15 to 30 degrees C, with 20 - 25 degrees C as their best growth temperature. These four Bdellovibrio only grew on live host bacteria rather than the dead ones. When 61 strains of bacteria were used as hosts, Bh04-4 lysed 21 strains, corresponding to 34.4% of lysis ability (21/61), Bh04-41a lysed 24 strains (39.3% lysis ability), Bh04-A + lysed 40 strains (65.6% lysis ability) and Bh04-1f 43 strains (70.5% lysis ability). Taken all four Bdellovibrio together, they lysed 55 out of 61 strains, amounting to 90.2% lysis ability. Results fully demonstrate the potential application of Bdellovibrio in lysing pathogenic bacteria from the marine environments.