The invention discloses a device and a method for nitrogen and phosphorus removal for low CN ratio urban sewage through nitrosation and anaerobic ammonia oxidation coupling denitrifying phosphorus removal intensification, and belongs to the field of biological sewage treatment. The device comprises an urban sewage raw water tank, a denitrifying phosphorus removal reactor, an adjusting water tank, a sedimentation tank, and an integrated partial nitrification and anaerobic ammonia oxidation reactor; when the urban sewage enters the denitrifying phosphorus removal reactor, phosphorus-accumulating bacteria utilizes organic carbon source in the urban sewage for anaerobic phosphorus release, sedimentation and water drainage are performed, the amount of output water is adjusted by the adjusting water tank, then the output water enters the integrated partial nitrification and anaerobic ammonia oxidation reactor, contained NH4<+>-N is converted into N2 to be effectively removed through partial nitrification and anaerobic ammonia oxidation, contained PO4 <3-> and a small amount of NO3<->-N produced in the anaerobic ammonia oxidation flow back with the output water to the denitrifying phosphorus removal reactor for denitrifying phosphorus removal, and then micro-aeration is carried out for a period of time. The method reduces oxygen consumption and energy consumption, improves the nitrogen and phosphorus removal rate, and avoids the problem of insufficient carbon source.