The design scale of an urban wastewater treatment plant (WWTP) upgrading reconstruction project is 12.0×104 m3/d. Its bio-chemical treatment is the Orbal oxidation ditch process. In order to determine the reconstruction scheme, based on the original Orbal oxidation ditch process, by analyzing the influent quality and the existing problems of WWTP, the methods of a deep bed filter added at the effluent end of the current secondary sedimentation tank, supplementing the carbon source, dosing the phosphorus removal agents and changing the disinfection mode are adopted, including the measures of constructing the deep bed filter tank together with its supporting structures as far as possible. The advanced treatment is the "deep bed filter + sodium hypochlorite disinfecting process". This reconstruction scheme has the advantages of small occupation of land, investment savings, little influence on the operation of WWTP, flexible operation mode, convenient operation and management. And the design effluent water quality has reached the level A standard of Urban Wastewater Treatment Plant Pollutant Discharge Standard (GB 18918-2002).