The utility model provides a joint structured reactor for flue gas denitration. When the reformation of SCR flue gas denitration is conducted on a thermal power boiler at the power station, the reformation is often limited by site restrictions such as the insufficient space on the tail of the boiler, resulting in the unreasonable arrangement of a denitration device and even the unachievable SCR flue gas denitration reformation; the distance from a vertical section flue at the inlet of a conventional reactor to the front wall of the reactor is approximately 2-2.5 meters; as the distance is only used for the arrangement of auxiliary support steel structure, the requirements for the layout space are high; when the layout room is limited, the adaptive capacity is poor. The reactor comprises a reactor body (3), wherein the reactor body is communicated with an inlet flue (1); the rear wall of the vertical section flue of the inlet flue shares a partition wall (2) with the front wall of the reactor body. The reactor provided by the utility model is used for flue gas denitration of the coal burning boilers at the firepower stations.