The invention discloses a preparation method of a polyurethane fiber with tensile fatigue resistance. According to the method, a screw-type nanotube is added to the polyurethane fiber for the first time. The method specifically comprises the following steps of firstly, using a high molecular surfactant and sonic oscillation treatment to do surface modification and dispersion processing on the screw-type nanotube, so as to prepare uniform and stable screw-type nanotube dispersion liquid; then uniformly mixing the dispersion liquid and other auxiliaries with a polyurethane solution; finally, forming the polyurethane fiber through a high-temperature channel evaporation solvent. According to the technical method, spring-effect of the screw-type nanotube is utilized to build a firmer elastic network structural system, so the tensile fatigue resistance of the polyurethane fiber is obviously promoted.