An object of the invention is to provide a denitrification action enhanced horizontal subsurface-flow constructed wetland system. The system comprises a water distribution ditch and a water receiving ditch which are arranged in the left and right sides of a substrate bed body, wherein a perforated water distribution plate is mounted between the water distribution ditch and the substrate bed body, a perforated water receiving plate which has the same structure as that of the water distribution plate is arranged between the water receiving ditch and the substrate bed body, a first water outlet pipe, a second water outlet pipe and a third water outlet pipe which are used for regulating water level are sequentially mounted on the right sidewall of the water receiving ditch from top to bottom, a water inlet pipe is mounted on the external sidewall of the water distribution ditch, a microporous aerator pipe is tiled at the bottom of the substrate bed body, the substrate bed body is provided with a first baffle plate and a second baffle plate, an ecological substrate frame mounting groove is formed between the first baffle plate and the second baffle plate, an ecological substrate frame is mounted in the ecological substrate frame mounting groove, and a plurality of hollow filler balls are mounted on the ecological substrate frame. According to the system, the structure is simple, novel and unique, the use and maintenance are convenient, the practicability is high, the operating cost is low, the denitrification capability of horizontal subsurface-flow wetland is greatly improved, the effect is good, and the economic and social benefits are remarkable.