The invention provides a small-sized integral multi-layer settling tank system. The system comprises a water distributor, settling tanks, a sludge discharge system, connecting pipelines and control valves, wherein the water inlet of the water distributor is connected with a water outlet pipe of a biochemical treatment process or physiochemical treatment process, and water produced from the biochemical treatment process or physiochemical treatment process flows into the settling tank through the water outlet of the water distributor; the sludge discharge system is connected with the sludge outlet of each settling tank; the settling tanks are distributed in a manner of a two-layer line, two two-layer lines, three two-layer lines or four two-layer lines, and the settling tanks are connected in parallel; and the water distributor is arranged above the upper settling tank. According to the small-sized integral multi-layer settling tank system, multiple defects of a single-layer settling tank can be avoided, the defect for setting multiple layers of settling tanks which are connected in series can be avoided, the shallow-layer settling principle can be effectively utilized, and solid load of sludge settling tanks under the same equipment limiting condition can be effectively increased.