The invention relates to a quadrate flange support based on a sewage treating system. The quadrate flange support based on the sewage treating system includes a support main body and tank walls, the upper side of the support main body is a flange positioning part, a long-strip-shaped groove is formed in the upper end of the flange positioning part and is used for being connected with a row of bolts at the lower portion of a quadrate flange, a height adjusting part in the middle of the support is of a retractable hinge structure, tank wall clamp parts are mounted on the tank walls, clamp platesand bolt sets are adopted to conduct positioning and fastening. The quadrate flange support based on the sewage treating system is suitable for positioning and supporting the quadrate flange and fixing the quadrate flange above the tank walls and is convenient to use and adjustable, all parts can be assembled and disassembled, so that replacement and maintenance are convenient.