A denitrification biofilter device, including: a regulating pool, a reactor body, a water tank, a first doser, a second doser, a backwash pump, a water inlet pump, and a blower. The regulating pool includes a raw water inlet and a water outlet. The reactor body includes a uniform water distributor, a filler layer, a buffer layer, a filter layer, a supporting layer, a filler supporting plate, a backwash water outlet, a treated water outlet, and a backwash water inlet. The treated water outlet and the backwash water inlet are disposed at the bottom of the reactor body and are connected to the water tank via pipes. The filler layer is filled with zeolites having a grain size of between 4 and 8 mm, a density of between 1.9 and 2.6 g/cm3, a porosity greater or equal to 48%, and a specific surface area of between 570 and 670 m2/g.