The invention relates to the field of denitration catalyst regeneration, and discloses a method for regenerating an arsenic poisoning deactivated denitration catalyst. The method comprises: (1) carrying out reduction washing on a denitration catalyst after physical ash cleaning, wherein the waste gas generated during the washing is introduced into an alkaline absorption pool through negative pressure, and is absorbed; (2) further carrying out deep reduction washing on the washed denitration catalyst, wherein the waste gas generated during the washing is continuously introduced into the alkaline absorption pool through negative pressure; and (3) drying the reduced denitration catalyst to prepare the regenerated denitration catalyst. According to the invention, the denitration activity of the deactivated denitration catalyst is recovered, the pollution on the washing liquid due to the introduction of a large amount of arsenic ions into the washing liquid can be avoided, the wastewater treatment difficulty is reduced, and the loss of a large amount of active components in the catalyst is avoided.