PURPOSE: To obtain the title fiber with large pore size through such processes that high-density polythylene and paraffin wax are melt-blended and the resulting melt is put into an extruder followed by melt spinning into undrawn yarn, which is then drawn under specified conditions and heat-treated followed by extracting and removing the paraffin wax.

CONSTITUTION: (A) 100 pts.wt. of high-density polyethylene 0.3-20g/10min in melt index and pref. ≥0.94 in density and (B) 30-300 pts.wt. of paraffin wax (pref. 50-70°C in melting point) are melt-blended, and the resulting melt is put into an extruder followed by melt spinning at a draft ratio of ≤200 into undrawn yarn. The yarn is then drawn by a factor of 1.4-4.5 at 60-120°C and a strain rate of ≤400%/min. Thence, the resulting drawn yarn is heat-treated followed by extracting and removing the paraffin wax, thus obtaining the objective fiber ≥30% in porosity.