The invention discloses a sewage treatment system, comprising a coarse grid, a fine grid, an adjustment pond, a primary sedimentation pond, an anaerobic pond, an anoxic pond, an aerobic pond, a secondary sedimentation pond, a coagulation reaction tank, a filtration section, a disinfection and high-speed centrifugal pond, an activated carbon pond and a water storage pond which are sequentially connected by pipes; the secondary sedimentation pond is downwards connected with a first control valve, part of the sludge generated by the secondary sedimentation pond is connected with a second control valve, and returns to the anaerobic pond through a returned sludge section, the other part of the sludge is connected to a third control valve, passes through a surplus sludge section and then is backwards connected with a sludge concentration room, a dehydration room, and a mud cake delivery section; the liquid outlet of the coagulation reaction pond is connected with the disinfection and high-speed centrifugation pond, the sediment outlet is connected with the surplus sludge section, the inlet of the anoxic pond is connected with a nitrification liquid tank, and the aerobic pond is also provided with a detection mechanism. The system and the method of the invention have the advantages of flexible and efficient process and excellent removal effect on various organic pollutants, especially nitrogen, combination of batch processing and continuous processing, and certain-extent automation.