The invention discloses a comb polyurethane associated thickener and a preparation method and an application thereof and the preparation method comprises the following steps: adopting primary amine and diglycidyl ether to react, obtaining hydrophobic diol; then adopting polyether diol, catalyst, diisocyanate, hydrophobic diol and alkanol to react, using precipitate for precipitation after finishing the reaction, drying the precipitation and obtaining the comb polyurethane associated thickener. More than two hydrophobic groups (long chain alkyl) in the molecules of the comb polyurethane associated thickener so that the consistency of the emulsion paint can be greatly improved, the emulsion paint has not only high viscosity under low shear but also low applicable viscosity under high shear, and the quality of the emulsion paint is increased. The polyurethane associated thickener is applicable to thickening the water-containing system and can be used in emulsion paint, varnish, adhesive, leather, papermaking, dyeing and printing, ink, cosmetics and the like.