A method for flue gas denotation includes the step of, in the presence of ammonia, enabling flue gas in a denitration reactor to pass through a plurality of catalyst beds from the bottom to the top to participate in a denitration reaction. Each catalyst bed contains a catalyst support component and a granular denitration catalyst stacked on the catalyst support component, and, in every single catalyst bed, the granular denitration catalyst moves along a same direction on the catalyst support component. Between every two adjacent catalyst beds, the granular denitration catalyst falls from the tail of a previous catalyst support component to the head of a next catalyst support component, making the granular denitration catalyst travel along the catalyst support components reciprocatively.