The invention relates to a preparation method of environmentally friendly printing ink polyurethane coupling agent. The invention is characterized in that vulcabond and polyester polyol are used to generate performed polymer with -NCO end group, then dimethylolpropionic acid and 1,4-butanediol are used to operate the chain extension reaction, finally, spasmolytol is used to adjust the pH value toneutrality, ethanol is added into the spasmolytol to be agitated, and then the printing ink polyurethane coupling agent is attained. The agglutination fastness of the coupling agent is strong, and thebinding strength of the printing ink and printing backing material can be obviously promoted. The invention has the advantages that no harmful solvent exists in the processing process. The inventionfully accords with the environmentally friendly technical requirements of chemical engineering accessory ingredient.