As a traditional industry plastic, polypropylene(PP) shows a tremendous application potential in many areas. However, the practical use of PP is mainly restricted to the low load-bearing environments because of its poor low-strain mechanical strength and stiffness. In this work, short kevlar fiber was introduced into PP matrix to improve its mechanical properties. In order to improve the dispersion of the fiber and enhance the interfacial interaction between fiber and matrix, a combination of ball milling and hosphoric acid treatment was used in this work. Pre-dried Kevlar fibers were soaked in hosphoric acid aqueous(0wt.%, 10wt.%, 20wt.%, 30wt.%) and milled for different time with various roller speed. It is interesting to observe that kevlar fiber can be easily exfoliated into several microfibers during ball milling, and the exfoliation has evident effect on the reinforcement effect because of the increase of interfacial adhesive area between the newly-formed microfibers and the PP matrix. Our work demonstrates that mechanical performance of short fiber reinforced plastic composites could be significantly improved by enhancing interfacial strength and fiber exfoliation using a facile surface modification strategy and conventional melt-processing technology.