Surface modification of Poly(ρ-phenylene terephthalamide) (PPTA) fiber has been considered an effcient way to increase the interfical bonding of the fiber/epoxy composites. In this article, the hydrogen peroxide solutions (H2O2) was used to treat the PPTA fiber based on an orthogonal experimental design. The optimum conditions of H2O2 treatment were concentration of 40%, treating temperature 40°C and treating time 60min. The morphology of the modified fiber were characterized by scanning electron microscope (SEM). The interfacial properties of aramid fiber/epoxy composites were investigated by the single fiber pull-out test (SFP. The results showed that the interfacial shear strength (IFSS) of aramid/epoxy composites was remarkbly improved which was attributed to the fact that some polar groups were introduced into the molecular structure of aramid fibers and the physical structure of the treated fibers was not etched obviously.