Fiber-matrix interfacial bond strength of composites is one of primary concerns for the prediction of composite behavior. including good mechanical properties and long retention durability. In this work. the effect of chemical surface treatment on Kevlar fibers has been studied in terms of the acid-base value and X-ray photoelectron spectroscopy(XPS). The mechanical interfacial properties of the final composites were also studied by critical stress intensity factor ( $K_{IC}$) and interlaminar shear strength(ILSS). Results showed that the chemical treatment conditions significantly affect the degree of adhesion at interfaces between fibers and the resin matrix. resulting in improving $K_{IC}$ and ILSS. This was probably due to the presence of chemical polar groups on Kevlar fiber surfaces, leading to the increase of interfacial binding force between fibers and the matrix In the composite system.m.