Haizhou Bay, an open bay in the west coast of Yellow Sea, is of an area of 900 km2, with hundreds of species (such as fish, shrimp, crab etc.) colonizing in the waters. As one of the 8 greatest fishing grounds in history, Haizhou Bay had even seen the maximum fishery catches of 50 000 t during the period of 1980s. However, due to the overfishing and destruction of spawning grounds and other habitats, fishery resources in Haizhou Bay have been declining from 1990s, with traditional economic species, such as hairtail, snapper sea bream, large yellow croaker, small yellow croaker as well as slender shad etc, not forming their regular fishing seasons. In order to improve fish habit at environment, and conserve fishery resources, the local government carried out a project of “Artificial Reef Construction in Haizhou Bay” from the beginning of 2002. As the first phase of the project, different types of concrete artificial reefs and vesselreefs with a total volume of 13 000 cubic meters were deployed in the middle part of Haizhou Bay (119°28′-119°29′14″E，34°55′-34°57′N) during the middle term of July, 2003, resulting in a fishing ground of about 10 km² area. So far, most studies on the habitat improvement function of artificial reefs have been qualitative, and very few quantitative researches have been reported. How to establish a certain quantitative relationship between building size of ARs and improvement degree of habitat is not only needed in evaluating artificial reef construction quantitatively, but also is one of the basic theories to decide scientifically the building size of artificial reefs in certain waters. As a trial of quantitative study on ecological benefits of artificial reefs, the variations of water quality, bottom mud as well as plankton etc was discussed. Between artificial reef area and near waters before and after the deployment of artificial reefs in comparative ways, according to the results of 4 surveys carried out in Haizhou Bay artificial reef area and near waters in 2003-2004. The survey result reveals that the upwelling produced by the deployment of ARs will bring nutritive salt such as nitrogen to upper levels, with the nitrogen content in bed mud in artificial reef area dropping to 85.7% of that before ARs deployment, while in the control area the content remains the same during the same season; at the same time, nutritional level indexes in AR area increase after ARs deployment, with 28.1% and 15.9% larger than that of the control area in autumn and winter respectively, therefore the water quality in AR area changes from nitrogen restriction (with an average P∶N value of 7.4) before to phosphorus restriction (average P∶N value of 20.9) after ARs deployment. As to plankton, the similarity index decreases from highly similar 0.963 before ARs deployment to 0.863 after 3 months of ARs deployment and 0.685 after 7 months of ARs deployment in AR area and control area. Community structure as well as habitat environment have changed a lot; at the same time, the individual weight of zooplankton has increase obviously by 5 times larger in AR area than in reference area, this is very good for proliferation of fishery resources. In conclusion, the amendment benefits of artificial reefs on ecological environment in certain waters have been proved quantitatively.