Abstract: Gelatinase,protease,amylase and phospholipase that were secreted by bacteria were all cell extracellular enzymes, which could conduct synergistic reaction with the hemolytic toxin in the bacterial pathogenesis. They could also decompose and destroy the tissue components of hosts, which was unfavorable for the growth of crab. In order to study the production situations of extracellular enzymes from Aeromonas in the water body of crab farming area in Southern Four Lakes, microorganisms in water body of this farming area were preliminarily separated and screened to obtain Aeromonas strain. This strain could produce extracellular casein protease,amylase,phospholipase and gelatinase and hemolysin outside , but it could not extracellular urease.