The invention discloses a selective catalytic reduction device for flue gas denitrification. The selective catalytic reduction device for flue gas denitrification comprises an NOx content detecting instrument, an NOx concentration detecting electrical sensor, a catalyst-paving porous bed and a catalyst/ fly ash separating device and also comprises an NOx removing device, a ventilating device, a ventilating plate, a catalyst regenerating instrument, a catalyst hopper and a catalyst conveying pipeline. A catalyst can be recycled when the fly ash is removed; air is inflated into the selective catalytic reduction device for the flue gas denitrification along a certain angle to blow off the fly ash falling on the catalyst, so that the problems that the catalyst cannot work normally due to poisoning caused by fly ash mixing and the increase of flow resistance of a catalyst layer can be solved; the NOx content detecting instrument can detect the concentration of NOx in flue gas denitrified by the selective catalytic reduction device in real time, and is connected with a ventilating port through the NOx concentration detecting electrical sensor; and when the NOx content is higher than a certain value, the ventilating port automatically ventilates to blow the fly ash, and when the NOx content is lower than a certain value, the ventilating port automatically closes, so that the automatism can be realized.