The invention discloses a low-specific-speed impeller and a design method for a blade of the low-specific-speed impeller. Both a front cover plate and a rear cover plate are of disc structures. The blade is designed according to the method that a column and twisting are combined, namely, a working face (4) or a back face (5) adopts a form of a backward bending column blade and the other side adopts a backward bending blade twisting mode, and therefore the blade accords with the law of fluid motion, reduces hydraulic loss, and improves efficiency of a low-specific-speed centrifuging pump. The thickness of the inlet edge, close to the front cover plate, of the blade is 2-3mm, the thickness of the inlet edge, close to the rear cover plate, of the blade is 5-7mm, and therefore sand mould casting lifting precision is improved, inlet flow passages can be partially blocked, and therefore blade inlet excluding coefficient is reduced, and the non-overload characteristic of the low-specific-speed centrifuging pump is improved. The low-specific-speed impeller and the design method for the blade of the low-specific-speed impeller can be applied to the field of efficient non-overload low-specific-speed impeller designing.