The development of composites using carbon fibers as the reinforcement requires surface activated carbon fibers with a durable surface composition. In this work, sized polyacrylonitrile (PAN)-based carbon ?bers were modi?ed by Oxy- Plasma treatment, Oxy- fluorination, and Nitric acid treatment in order to improve the interaction between carbon ?ber surface and matrix. The effect of different surface treatments was observed by means of contact angle, surface free energy measurement. Surface roughness were seen by the help of Scanning electron microscopy (SEM).The lower contact angle proved the surface hydrophilicity of treated carbon fiber.XPS, Zeta-potential measurements revealed changes in surface chemistry of treated carbon fibers. The higher tensile strength of activated carbon fibers gave the assurance of more load bearing capacity of carbon fibers and also the acceptability of activation process.