The invention discloses a reactor device for realizing the denitration reaction and regeneration of a selective catalyst reduction (SCR) catalyst. The device comprises a reactor and a circulating pool, wherein a first three-way adapter valve which is connected with a flue gas input pipeline is arranged at an inlet of the reactor; a second three-way adapter valve is arranged between the reactor and the circulating pool; and through a circulating pump, the circulating pool is communicated with a third three-way adapter valve and then is communicated with the first three-way adapter valve. The invention also discloses a process for realizing the denitration reaction and regeneration of the SCR catalyst, wherein the denitration reaction of the SCR catalyst and the regeneration process of the SCR catalyst can be alternately performed in the same reaction device. A regeneration reaction device for the SCR catalyst and a denitration reaction device for the SCR catalyst are fused into one reaction device, the investment cost of equipment is effectively reduced, working procedures and expenses of the detachment and reinstallation of the SCR catalyst are avoided, and tim and labor are saved. Meanwhile, the process greatly reduces the using amount of acid solution and main agent supplement solution in regenerative raw materials.