The invention discloses a sewage treatment system. The sewage treatment system comprises a rotational flow grit chamber, periodic circulation activated sludge tank, a contact disinfecting tank, a sludge thickening tank, a pretreatment unit, a pre-thickening unit, an evaporation unit, a crystallization unit, a condensate fine treatment unit and a solid content treatment and recovery unit, wherein a suspended filler is provided in a pre-reaction zone of the periodic circulation activated sludge tank; the pretreatment unit comprises a high-density sedimentation tank, a V-shaped filter, an advanced oxidation subunit and an ultrafiltration subunit; the pre-thickening unit is provided with a reverse osmosis membrane thickening system; the evaporation unit is provided with a falling film evaporation system; and the crystallization unit is provided with a forced circulation crystallization system. The sewage treatment system disclosed by the invention realizes zero discharge of salt-containing sewage, completely eliminates sewage discharge to adjacent water bodies, has the advantages of high pollutant removal efficiency, compact land occupation, high automation level, stable running, low investment, low running expense and the like, and can well adapt to water quality of low temperature salt-containing sewage, and effluent water can stably reach a standard for reclaimed water recycling.