Poly(vinyl alcohol)(PVA) was dissolved in DMSO(dimethyl sulfoxide) and m-aramid was dissolved in DMAc(dimethyl acetamide). The composite fibers were prepared by wet-spinning a mixture of the m-aramid and PYA solutions with methyl alcohol as a coagulant. The ratio of m-aramid to PYA was 10/90, 20/80, 30/70, 40/60, 50/50 wt%. The composite fibers had sea-island bicomponent structures; the island component was m-aramid and the sea component was PYA. The nano-sized m-aramid fibers were obtained by washing out PYA with boiling water. Phase separation in theses immiscible polymer solution blends led to m-aramid being extracted in a nano-sized fiber state. The diameter of the fibrillated m-aramid fibers decreased as the PYA contents increased (130~313 nm). This study provided a new method to make nano-sized m-aramid fibers with wet-spinning.