NOVELTY - Construction of benthonic microorganism layer on substrate sludge layer of eutrophication water comprises cleaning natural shells, baking at 300-500 degrees C, and immersing in an acid solution to remove organic material and activate gaps on surface of the shell, preparing carrier; immersing the pretreated shell into a nitrifying tank of city wastewater to carry microorganism; laying the carrier of benthonic microorganism on substrate sludge layer of eutrophication water; and setting an aeration system over the carrier of benthonic microorganism.    USE - The method is for constructing benthonic microorganism layer on substrate sludge layer of eutrophication water (claimed). It is useful for controlling substrate sludge pollution of eutrophication water.    ADVANTAGE - An inorganic mineralized stable layer is formed on the substrate sludge layer through the mineralization effect of carrying microorganism to the organic material and nutrient salt within the substrate sludge layer, such that release of nutrient salt within substrate sludge layer can be controlled. The method is simple and easy; and has low investment.    DETAILED DESCRIPTION - Construction of benthonic microorganism layer on substrate sludge layer of eutrophication water comprises taking shells as carrier of benthonic microorganism; cleaning natural shells, baking at 300-500 degrees C, and immersing in an acid solution to remove organic material and activate gaps on surface of the shell, preparing carrier having a stacking density of 0.9x 103-1.2x 103 kg/m3 and specific surface area of 10-50 m2/kg; immersing the pretreated shell into a nitrifying tank of city wastewater to carry microorganism, taking out, and standing for 3-10 days; laying the carrier of benthonic microorganism on substrate sludge layer of eutrophication water, where amount of carrier per m2 of substrate sludge layer is 0.5-1.0 kg; and setting an aeration system over the carrier of benthonic microorganism, promoting mineralization of carried benthonic microorganism to the substrate sludge layer by supplying oxygen, and transferring and removing nitride.