The invention relates to the technical field of textile wastewater treatment, in particular to a secondary sedimentation tank. The secondary sedimentation tank comprises a tank body, a sludge scrapingassembly, a bridge frame, a rotation part and a flocculating assembly, the sludge scraping assembly is arranged on the bottom of the tank body, the bridge frame is arranged on the top of the tank body, the rotation part is arranged at the central axis of the tank body and used for driving the sludge scraping assembly and the bridge frame to rotate, and the flocculating assembly comprises an annular air inlet column and a suction part which is connected with the drive shaft of the rotation part; multiple air inlet hole channels are formed in the air inlet column, and the outer side face of theair inlet column is connected with the inner wall of the tank body through a connection rod; an arc baffle is arranged on the bottom of the outer side face of the air inlet column, and multiple through holes are formed in the arc baffle; the suction part comprises an L-shaped connection part which is connected with the drive shaft of the rotation part and a fan blade part which is connected withthe connection part, and the end of the fan blade part abuts against that of the arc baffle. The secondary sedimentation tank can treat textile wastewater containing light fiber impurities.