The invention discloses a biofilm enhanced denitrifying device. The biofilm enhanced denitrifying device mainly comprises a main reactor and a sedimentation tank, wherein the main reactor mainly comprises an outer barrel, an inner cavity I, an inner cavity II and a top cover; the interior of the outer barrel is divided into an upper layer and a lower layer; the inner cavity I and the inner cavityII form a central symmetrical structure, and are positioned in the upper layer and the lower layer of the interior of the outer barrel respectively; when the biofilm enhanced denitrifying device works, the main reactor is filled with a biological filler with the volume fraction of 10-30%; the biological filler comprises porous materials with different particle sizes. The biological filler is usedfor supporting and being adhered to a biofilm and optimizing a microecological environment, layered internal circulation inside the denitrifying device and partitioned control of dissolved oxygen, microbial species and the sludge concentration are achieved, optimization on spatial distribution and large-scale accumulation of many types of denitrifying functional microbes is facilitated, and the activity thereof is fully played; the biofilm enhanced denitrifying device has the characteristics of a compact structure, low cost, simple operation, easiness in control, unlikeliness in sludge loss, low energy consumption and stable long-term operating performance.