The invention relates to a method for preparing polyurethane finish paint for a wind force blade. The method mainly comprises the steps of: firstly, sequentially adding resin capable of reacting with isocyanato, rutile type titanium dioxide, a weather-resistant assistant, an antistaining assistant, a nanometer additive, a dispersant, a defoaming agent, a rheological additive, an anti-settling agent, a leveling agent and a catalyst into a mixing tank respectively, and dispersing and grinding an obtained mixture to achieve the granularity being lower than 50 micrometers; then, adjusting the viscosity by using an environment-friendly organic solvent, and mixing colors by using color paste; and mixing two kinds of polyurethane curing agents for full reaction. The invention has the beneficial effects that the prepared polyurethane finish paint is excellent in wind and sand resistance as well as rainfall erosion resistance and has a wide applicable range, and the method is favorable for increasing the elongation rate of the polyurethane finish paint to be more than 10%.