Abstract: Traditional electroless nickel plating on carbon fibers concerns the use of PdCl2-SnCl2 activation pre-treatment, which can be costly and requires extended process lines with high consumption of noble metal palladium. A new pretreatment process of electroless nickel plating on carbon fibers is proposed in this paper, using palladium-free activation. The effects of nitric acid processing time on the quality of nickel coating is studied and the optimal processing time is determined to be 30min. The effects of the concentrations of Ni2+ on the rate of weight gain during Ni2+ complexing adsorption process is analyzed, the kinetic equation of the process is established, and the reaction equilibrium constant K is determined as 2.525. The theoretical values calculated by the equation are basically consistent with the experimental data. The effects of the reaction temperature on P content in the Ni-P coating are discussed. P content reaches a maximum value 11.42% at temperature of 80℃. Materials characterizations of the deposited layers are analyzed by SEM, EDX and XRD. The experiment results show that the nickel deposit on carbon fiber obtained by this KBH4-NiSO4 method is as uniform, compact, adhesive and antioxidant as that obtained by conventional electroless nickel plating.