The invention discloses a preparation method and application of high-solid-content water-based polyurethane resin and coating thereof. The preparation method comprises the following steps: reacting poly (propylene carbonate) polyols or a mixture of poly (propylene carbonate) polyols and other conventional polypolyols with isocyanate, a chain extender, a crosslinking agent, a catalyst and a sulfonic acid type hydrophilic chain extender, adding water to perform emulsification, and removing a solvent to obtain the high-solid-content water-based polyurethane resin; adding aids such as a leveling agent, a thickening agent, color paste, an environment-friendly cosolvent and a defoaming agent to obtain high-solid-content water-based polyurethane resin coating prepared from the poly(propylene carbonate)polyols. Film-forming and drying speed is high, plumpness is high, and high adhesive force, hardness, water resistance and solvent resistance are achieved.