The utility model discloses a device for removing nitrogen oxide in flue gas based on a biological packing tower, which comprises a biological packing tower. The biological packing tower comprises an outer shell, a top cover and a bottom cover are respectively arranged at the upper end and the lower end of the outer shell; an air outlet and a water inlet are formed on the top cover; an air inlet and a water outlet are formed on the bottom cover; a spray nozzle, a liquid distributor and a filling material are arranged inside the outer shell; the spray nozzle is connected with the water inlet through a pipe line; a fluid reservoir is arranged below the biological packing tower; the water outlet is connected with the top part of the fluid reservoir through a pipeline; and the water inlet is connected with a water pump and the bottom of the fluid reservoir through a pipeline. In the utility model, the fluid reservoir is arranged below the biological packing tower so as to realize the circling treatment of the flue gas containing nitrogen oxide. The device of the utility model has the advantages of simple structure, convenient operation and industrialized application prospect.