Abstract: An associated heterotrophic dominant single bacteria-Z-QS01 was selected to study its mechanism of quorum sensing and factors that affected quorum sensing using ecotoxicological technique in co-cultural system with Chlorella vulgaris. The results show that self-regulation and inhibitive effect of bacteria-Z-QS01 to Chlorella vulgaris could implement through excreting chemic substance. Density of bacteria-Z-QS01 and concentration of chemic substance excreted by bacteria-Z-QS01 are the necessary conditions, which decide whether the regulation mechanism could be carried out or not. The enhanced UV-B radiation could affect quorum sensing of bacteria-Z-QS01 significantly, and the inhibitive effect to Chlorella vulgaris is decreased gradually with the dose increase of UV-B radiation.