Abstract: Carbon fibers with a carbon content of over 90% have the characteristic of strong surface inertness, so surface activation treatment is an essential process in their preparation. The effect of current intensity on the physicochemical structure and properties of electrochemically activated carbon fiber surface under dilute H₂SO₄ electrolyte were explored by XPS, Raman, dynamic contact angle, monofilament tensile strength and interfacial shear strength, and non-contact anodizing device was used. The results show that the content of oxygen-containing functional groups increases by the attack of reactive oxygen O on the surface of carbon fibers, and the activation effect is significant with increasing current within the scope of this study. Carbon fibers near the anode are affected by static electricity and diffusion. SO₄ ²⁻ and S₂O₈ ²⁻ enter the internal gap of carbon structure, so the surface S/C and diameter of carbon fibers increase. Under the action of SO₄ ²⁻ etching, the disordered carbon structure on the surface of carbon fiber fell off, the degree of graphitization decreases. SO₄ ²⁻ and S₂O₈ ²⁻ are intercalated into the carbon structures, forming an associated structure through electrostatic interaction. Under the combined effect of etching and intercalation, the monofilament tensile strength of carbon fibers has been improved, with a maximum increase of 16.77%. After 0.5 A current treatment, the surface roughness of carbon fiber is improved, the content of hydroxyl and carboxyl functional groups on the carbon fiber surface that can react with the epoxy resin matrix is the highest, the surface polarity of carbon fiber is the strongest, the dynamic contact angle with deionized water is reduced from 89.9° of untreated to 50.6°, and the corresponding interfacial shear strength of the composite is increased by 47.70%.