Glycidylmethacrylate and divinylbenzene were copolymerized in a n-hexane solution of poly(propylene-co-1-butene). The resultant polymer composite contains fine particles of poly(glycidylmethacrylate-co-divinyl benzene). This composite was blended with polypropylene. Next, the resultant polypropylene composites were melt spun and stretched. Microporous polypropylene fibers were thus prepared and their properties were evaluated.