The invention discloses a low-energy-consumption sanitary sewage treatment system. The low-energy-consumption sanitary sewage treatment system is characterized by comprising a primary pretreatment part, a secondary biochemical treatment part and a tertiary deep treatment part which are connected through sewage pipes in sequence, wherein the primary pretreatment part comprises a grid well and an adjusting tank; the secondary biochemical treatment part comprises an enhanced external circulation anaerobic reactor, a water distributing well, a sedimentation tank and a sludge dewatering pump room;the tertiary deep treatment part comprises a two-stage tower type biological filter tank, a dephosphorization reaction sedimentation tank, a disinfection tank and a filter device. The low-energy-consumption sanitary sewage treatment system is high and stable in sanitary sewage treatment efficiency, low in energy consumption, low in sludge output, low in space occupation and suitable for up-to-standard treatment and deep treatment of sanitary sewage from large, medium and small towns.