The test organisms (Paralichthys olivaceus ) were exposed to CB- 28 with different spiked concentrations. After 72 h, EROD activities in livers of the test organisms were measured. It was found that EROD activities significantly mounted up with the increase of spiked quantity. Therefore, there existed a dose-response relationship between EROD activities and specific pollutant concentrations. In the meantime, the optimal conditions for the analysis of EROD activity were discussed. The limitation of EROD activities as a monitoring parameter was also analyzed.