The invention relates to a sludge concentration multiplier. The sludge concentration multiplier comprises a settling tank and an outer-layer isolation tank, wherein the settling tank is arranged in the outer-layer isolation tank, and a water distribution chamber is arranged between the settling tank and the outer-layer isolation tank; the settling tank comprises a conical water distribution part, a suspended sludge layer and a settling region; holes are formed in the bottom of the water distribution part, and a water distribution guide plate is arranged inside the water distribution part; the suspended sludge layer is located above the water distribution part, the settling region is located above the suspended sludge layer, and an inclined tube is arranged in the settling region; a conical collection part is arranged at the bottom of the outer-layer isolation tank, and a sludge concentration control board is arranged at the bottom of the collection part; and a water inlet is formed in the outer wall of a near end of the top of the outer-layer isolation tank, and the water inlet is communicated with the water distribution chamber. For overcoming defects of BOD and COD operation modes during sewage degradation in the conventional technology, the sludge concentration multiplier provided by the invention has the advantage that mud-water separation is carried out in an aerobic tank synchronously, so that the aims of refluxing sludge and increasing sludge concentration are achieved.