Abstract: In order to study the differences of extracellular enzymes （protease, amylase, lipase, urease） of heterotrophic bacteria in the water body and sediment in cultured area and non--cultured area of crabs in Weishan Lake,microbe in these two environments were preliminarily screened out and separated. And 25 bacterial strains were obtained, cultured and observed on the solid culture media that contained protein, fat, starch and urea. The colonies were recorded and the size of antibacterial circle was measured. The results showed that the bacteria that produced protease and lipase in cultured area of crabs were more than that in non-cultured area of crabs, but the amount of the bacteria that produced amylase and unease had little difference.