The utility model relates to a miniature decentralized sewage treatment unit. Sewage treatment plant include that overflow distribution well and the domestic sewage of decentralized peasant household who sets up on overflow distribution well both sides are detained the cell, sewage be detained be equipped with inlet tube and outlet pipe in the cell and feed through distribute the well to the overflow in, the aboveground portion of overflow distribution be equipped with adjustable overflow weir, overflow distribution well distribute the well wall of a well for the overflow outward, the overflow distribution well wall of a well be the spirochaeta form, overflow distribution well inner chamber top -down grow gradually. The utility model discloses simple structure, clean effect are good, reaction, attaching space are big, nos consumption of power, biodegradable are effectual, and the overflow distribution well wall of a well is the spirochaeta form, does benefit to the inorganic filth of solid sediment, sewage is detained the cell and divides six layers, is maze intestinal formula, and the curved tube is designed into on upper portion to encircle overflow distribution well, make the microorganism to abundant attaching space of organic matter and sufficient digestion time.