The invention relates to the field of concrete additives and specifically relates to a mud content inhibitor for concrete doped with a polycarboxylic acid type water reducer and a preparation method and an application method of the mud content inhibitor. The mud content inhibitor is prepared by the following raw materials of, by weight, 20%-30% of mud dispersion components, 0.5%-5% of mud adsorption components, 0.5%-5% of ion complexation exchange components and the balance water. The preparation method includes firstly, uniformly stirring water and the mud dispersion components, and adding and uniformly stirring the mud adsorption components and the ion complexation exchange components. The application method includes that the usage amount of the mud content inhibitor is 2-5 wt. % of that of the polycarboxylic acid type water reducer. By means of the mud content inhibitor, the liquidity and the slump-retaining performance of the concrete can be increased, the viscosity of the concrete is reduced, the work state of the concrete can be improved, the adsorption quantity of high valence metal ions to the polycarboxylic acid type water reducer can be reduced, and the performance of the concrete doped with the polycarboxylic acid type water reducer is guaranteed.