The invention relates to the technical field of water pollution control, particularly a method for treating black and odorous water by using ethanol making straw waste residue immobilized phosphorus-accumulating bacterium. The method comprises the following steps: 1) treating ethanol making straw waste residues by using subcritical water to increase the porosity and specific area; 2) extracting activated sludge, and carrying out culture and domestication to obtain high-activity denitrifying phosphorus-accumulating bacterium; 3) adsorbing the denitrifying phosphorus-accumulating bacterium obtained in the step 2) by using the ethanol making straw waste residues obtained in the step 1); 4) covering a polyvinyl alcohol water solution on the ethanol making straw waste residues with adsorbed denitrifying phosphorus-accumulating bacterium in the step 3); and 5) dispersing the ethanol making straw waste residues obtained in the step 4) in a cage tank, and putting the ethanol making straw waste residues in a river course to be treated. The method can effectively enhance the oxidation-reduction potential of the black and odorous water only by periodically adding and replacing the cage tank without adding any chemical agent; and meanwhile, the method implements denitrification and dephosphorization on the black and odorous water, lowers the chroma and turbidity of the black and odorous water, and inhibits the odorous gas from emission.