Double-sided polishing die and polishing method for square glass

The invention discloses a double-sided polishing die for square glass and a polishing method, the double-sided polishing die comprises a clamp and a fixed chassis, the clamp is provided with a plurality of rectangular grooves distributed in a central symmetry mode, and the rectangular grooves are matched with the square glass. The fixed chassis and the clamp are arranged, the first inner side edge and the first outer side edge of the clamp are parallel, the second outer side edge and the second inner side edge of the clamp are parallel, the fixed chassis comprises the first side plate and the second side plate which are perpendicular, and when the clamp is fixed to the first side plate, the second outer side edge abuts against the inner side wall of the second side plate, so that the perpendicularity of a polished surface is guaranteed; when the clamp is fixed to the second side plate, the first outer side edge abuts against the inner side wall of the first side plate, and the perpendicularity of the polished