The invention relates to a novel preparation method of polyoxymethylene fiber, in particular to the novel preparation method of the polyoxymethylene fiber via multi-stage slow cooling and three-stage drawing with different media, which comprises the following steps: vacuum-drying polyoxymethylene granular materials, heating and melting via a screw extruder, melting and extruding by a spinneret, leading small melt flow to pass through the multi-stage slow cooling, carrying out high-speed traction, passing through a moistening and oiling cluster, winding, then obtaining as-spun fiber, carrying out hot air drawing and two times of drawing with different types of solvent, then carrying out hot molding and finally preparing the polyoxymethylene fiber. The novel preparation technology can solve the problems of matching between the multiple sections of atmosphere and temperature and the spinning process control and the control of the drawing with multiple media and make up for the deficiencies that the single atmosphere and temperature and the single medium drawing of the prior art lead the structure to be difficult to stable and uniform.