Gravity-driven distributed rural sewage treatment system and method

The invention discloses a gravity-driven distributed rural sewage treatment system. The system comprises a grating tank, an anaerobic tank, a multi-stage soil infiltration system and a stepped subsurface flow constructed wetland which are sequentially communicated through a pipeline and are distributed in a stepped manner, the grating groove is used for filtering out floating or suspended pollutants; the anaerobic tank is used for degrading macromolecular organic matters under an anaerobic condition; the multi-stage soil percolation system is used for removing nitrogen and phosphorus and adsorbing and degrading small and medium molecular organic matters; the stepped subsurface flow constructed wetland is used for removing the eutrophic elements in the water body. The invention further discloses a gravity-driven distributed rural sewage treatment method. The landform characteristics are fully utilized, so that each system of the ecological filter bed has a certain height difference, water flow is driven by gra