The invention discloses a modularized buried sewage treatment system which comprises a concrete bottom slab and a PP module, wherein the strength of the concrete bottom slab is C25, a concrete cushion with the strength of C25 is arranged below the concrete bottom slab, a sand cushion or wide mellow sand is arranged on the upper surface of the concrete bottom slab, the PP module consists of a plurality of blocks, a compound seepage-proofing membrane is arranged on the outer surface of the overall PP module, a geotextile layer is also covered above the compound seepage-proofing membrane on the upper surface of the PP module, the PP module is a cuboid box body, and the interior of the PP module is sequentially separated into a closed anaerobic tank, an aerobic tank, a settling tank, a sludge tank and a disinfection tank by partition boards. Compared with the traditional equipment, the modularized buried sewage treatment system is wide in application range and can work and run only by connecting with a pipeline without the need of civil engineering, so that the land occupation, cost and construction period can be greatly reduced; and the modularized buried sewage treatment system has a novel design and a compact structure, is convenient to transport, and is not afraid of corrosion, and the service life is prolonged.