Sphagnum artificial wetland sewage treatment system

The utility model discloses a sphagnum artificial wetland sewage treatment system, which comprises a primary sedimentation unit, a peat pool module or a sphagnum filter, a porous medium filter, a subsurface wetland module and a discharge unit, the peat pool module or the sphagnum filter comprises at least one peat filter pool, and the porous medium filter comprises at least one porous medium filter. The peat filter is composed of a sphagnum peat bed, a plurality of first perforated pipes are arranged in the sphagnum peat bed, four-stage purification of sewage is achieved, and purified water is discharged into a natural water system or underground soil. The elevation of the peat pool module is larger than that of the porous medium filter and larger than that of the subsurface flow wetland module, and sewage can flow automatically by means of gravity. The sewage treatment process comprises the following steps: sewage firstly passes through the primary settling unit to remove settleable solids and suspended soli