Abstract: From the point of view bacteriology, the author suggested that microorganism activities in the aquatic system of cage aquaculture not only reflected the produc-tivity of the cage aquaculture, but also involved with the environmental effect. This paper discussed in particular about the distribution of bacteria in the aquatic system of cage aquacuiture. It also showed in detail the field test results and their statistical analysis, the standards ior the determination of pollution level, the characteristics of temporal and spacial distribution of pollution induced by bacteria, and so on.