Efficient denitrification sewage treatment system

The utility model belongs to the technical field of sewage treatment, and particularly relates to an efficient denitrification sewage treatment system which comprises a mixing device, an anaerobic tank, an anoxic tank, an aerobic tank and a settling tank which are arranged in sequence, a sludge return pipe is connected between the bottom of the sedimentation tank and the lower part of the anaerobic tank; the mixing device comprises a mixing tank, a piston cylinder and a stirring mechanism, and a sewage inlet pipe is connected to the mixing tank; a piston is slidably connected into the piston cylinder and connected with a piston rod. A feeding pipe and a discharging pipe are connected to the piston cylinder, a one-way feeding valve is arranged on the feeding pipe, and a one-way discharging valve is arranged on the discharging pipe; the stirring mechanism comprises a stirring rod and a motor, and stirring blades are arranged on the stirring rod; a cam capable of driving the piston rod to reciprocate is arranged