: Composites made of polymer resins reinforced high performance fiber, such as carbon fiber, are widely used in various industries, including aerospace industry, due to their special properties such as strength and high modulus and low weight. One of the problems of these composites is the weakness of the interlayer properties due to the poor mechanical properties of polymer resin. To overcome this problem, additional factors such as nano materials are added to the polymer resin. New way to improve interlaminar properties is electrospinning of nanofibers on the reinforcing fibers directly. In this study, the effect of adding nanofiber layers polyacrylonitrile and polyacrylonitrile reinforced with alumina nanoparticles on the tensile and flexural properties of epoxy/carbon composite was investigated. Alumina nanoparticles were used to strengthen the mechanical properties of polyacrylonitrile nanofibers. As alumina nanoparticles were added to polyacrylonitrile nanofibres in various weight percentages and nanofibres were produced by the electrospinning process. Mechanical properties and morphology of nanofiber were studied by tensile and scanning electron microscopy test. The results showed that the addition of alumina nanoparticles up to 2 wt% increased the tensile strength and then reduced the properties of nanofiber due to the accumulation of nanoparticles. The accumulation of nanoparticles was observed in scanning electron microscopy images. The best result was obtained in 1% wt of alumina nanoparticles, which increased the tensile strength of nanofibers by 31.32%. Also, the addition of alumina nanoparticles increases the diameter of polyacrylonitrile nanofibres by increasing the viscosity of an electrospinning solution. The diameter of polyacrylonitrile nanofibers increased by adding 1 wt% of alumina nanoparticles from 219 to 237 nm, and the viscosity of electrospinnig solution increased by 7.4%. Subsequently, poly acrylonitrile and polyacrylonitrile/Alumina nanofibers were electrospinning directly on carbon fiber and their effect on the tensile and flexural properties of the composite was investigated. The results showed that the addition of polyacrylonitrile nanofibers layer in the between composite layers increased 14.5% and 12.14%, respectively, in the tensile and flexural strength compared the control composite. Also, the addition of polyacrylonitrile/Alumina nanofibers layer increased the tensile and flexural strength of the composite by 19.47% and 20.07%, respectively, compared to the control composite. The results of the fracture surface of the composites studied by the scanning electron microscope showed that the composites containing nanofibers had a roughness fracture surface. Keywords: Composites, electrospinning, polyacrylonitrile nanofibres, alumina nanoparticle