PURPOSE: To produce polyolefinic reticular fiber, excellent in strength and opening properties and suitable for producing a flash spun nonwoven fabric sheet by using a noncombustible halogenated hydrocarbon having remarkably low ability to destroy the ozonosphere.

CONSTITUTION: The objective method for producing polyolefinic three- dimensional fiber is characterized by using a mixed solvent composed of a good solvent selected from the group consisting of trichloroethylene, tetrachloroethylene, fluorotrichloroethylene and 1,1,2-trichloro-3,3,3- trifluoroethylene and a cosolvent, selecting the cosolvent from the group consisting of carbon dioxide, sulfur hexafluoride, chlorodifluoromethane and 1,1,1,2-tetrafluoroethane for a polyolefinic solution and regulating the weight ratio of the polyolefin to the solvent in the polyolefinic solution to 5-25wt.% in a method for producing the fibrillated polyolefinic three-dimensional fiber by passing the polyolefinic solution prepared at a high temperature under a high pressure through a vacuum orifice, a vacuum chamber and a spinneret and releasing the resultant solution to a zone at ordinary temperature under atmospheric pressure.