The invention provides an anti-mud functional admixture for concrete, and belongs to the technical field of concrete admixtures. The general formula of the admixture is as shown in the formula I whichis as shown in the specification; in the formula I, R is selected from -OCH2CH2O-; m, n and g are all integers; m and n are selected from 1 to 10; g is selected from 1 to 8. A preparation method forthe admixture provided by the invention comprises the following steps: adding epichlorohydrin and a catalyst into a reaction container; stirring and dissolving, adding hexamethylenetetramine and polyethylene glycol, continuously stirring, cooling after the reaction is ended, and adding water for diluting to obtain the anti-mud functional admixture. According to the preparation method, a block copolymer of cations and polyethylene glycol is prepared by utilizing a ring-opening reaction of the hexamethylenetetramine, the epichlorohydrin and the polyethylene, so that the adsorption and dispersioneffect to clay can be improved; meanwhile, the expansion of the clay can be inhibited; the compatibility with an anionic polymer PCE can be improved; the adaptability to different clays can be improved. According to the anti-mud functional admixture for the concrete, and the preparation method and the application thereof, raw materials are cheap and easily obtained; the reaction conditions are mild; the synthesizing process is simple and convenient; a reaction solvent is not required to be added additionally; the anti-mud functional admixture for the concrete is suitable to be popularized.