The invention discloses a denitrification filter tank which comprises a denitrification filter tank body, a water inlet pipe, a mixing tank, a water distribution channel, a water distribution weir, a water outlet channel, a back-washing air blower, a back-washing water pump and the like. According to the denitrification filter tank provided by the invention, uniform water distribution of the denitrification filter tank body is realized through the design of the water distribution channel, the water distribution weir and a gate, and an input water source is uniformly distributed; and by arranging a feed forward-feedback composite control system, accurate feeding of a carbon source is achieved, the operation cost is reduced, and the management complexity is simplified. In addition, the problems of filler hardening, low concentration of a biological membrane of a filter material layer, low denitrification load, easy generation of air resistance and the like which exist for a long time in the prior art are solved, and the effluent quality is greatly improved.