The invention discloses a modular sewage treatment system which comprises a regulating tank, a primary sedimentation tank, an anaerobic tank, an oxygen-deficient tank, an aerobic tank, a secondary sedimentation tank, a filter tank, a disinfection well, a sludge tank and an air blower well. Modules are communicated with one another via pipelines, a sewage treatment working procedure can be independently completely carried out by each module, and the various modules work with one another, so that the integral modular sewage treatment system and an integral modular sewage treatment device can be formed. The modular sewage treatment system has the advantages that the modular sewage treatment system is high in technical integration level, compact in structure and small in occupied area, various treatment units are highly combined with one another, and the investment can be effectively reduced; the modular sewage treatment system is in a modular design, the various modules can be prefabricated in advance and can be quickly spliced in fields, accordingly, the design and construction periods can be shortened, technologies can be flexibly combined with one another, the modular sewage treatment system is wide in application range and high in impact load resistance and can effectively cope with change of the water quality of different types of raw water, sewage can be cooperatively treated by the diversified technologies including activated sludge processes and biological membrane processes, and nitrogen and phosphorus removal effects of the modular sewage treatment system can be improved; the modular sewage treatment system only comprises few electric facilities, is low in energy consumption and high in automation degree and can be operated under unattended conditions, and accordingly management burden can be relieved.