Abstract: The surface bonding ability of poly-p-phenylene benzobisoxazole (PBO) fibers is weak, and its interface strength after being compounded with resin is low, which affects the mechanical properties of composite materials. This research coated the PBO plain weave fabric with a layer of polyacrylonitrile (PAN) nanofiber membrane by electrospinning. The composite material was subsequently obtained by layering and curing, which formed a gradient interface between the PBO fibers and the epoxy resin to improve the interface strength of composite materials. The short beam shear test of composites was carried out by universal testing machine, and the best interlayer performance enhancement effect was determined by changing the spinning voltage. The relative stiffness image in interface was obtained with atomic force microscope (AFM) to investigate the enhancing mechanism of interface strength. The results show that when the spinning voltage is 20 kV, the interlaminar performance of the composite is most obvious under the condition that the pushing speed of the syringe pump and the rotating speed of the collecting roller remain unchanged. Compared with the pure PBO fibers reinforced composites, the interlaminar shear strength of the PBO fiber reinforced composites coated with film is increased by 40.1%. The gradient interface structure helps to transfer the stress evenly from the resin matrix to the fiber reinforcement and improve the mechanical properties of the composites.