The purpose of this study is to added the surface area of poly (P-phenylene-2, 6-benzobisoxazole, PBO)fiber, and get the good efficiency on interfacial character between fiber and rubber. In this study, using electron beam irradiate by changing the accelerate voltage and dosage of electron beam to added the surface area. Observe the surface change by SEM and Raman spectroscope. Then the tensile strength and the adhesive force between fiber and rubber will be carried out to examine the effect of treatment. The results show that, 800kY, 10Mrad get the best adhesive force between fiber and rubber, increase 34%, and tensile strength of fiber decrease 13%.