The cross section of the spinneret is a rectangular spinneret hole. The polypropylene filament is sprayed out by the spinneret and cooled rapidly by the cooling water mist of about 4OC from the atomizing nozzle. The heat insulation plate prevents the water mist from spraying onto the spinneret. The water guide tank is used to collect the condensate water from the top and adjust the width of the valve to facilitate the hanging of the condensate water on the polypropylene filament. The polypropylene filament is oiled on the oil roller and then sent to the hot roll below. Reheat the draft. Because the number of spinneret holes is small, the spurted yarn is thick and the cross section is rectangular, the cooling speed and rigidity of polypropylene filament are improved, and the special high strength polypropylene filament can be produced.