Bioactive calcium phosphate coating was prepared on C/C composites by sonoelectrodeposition technique. The analyses by SEM, XRD, FRIR and EDS show that as-received coating exhibiting subtle net-like morphology is composed of carbonate hydroxyapatite with the Ca/P ratio of 1.64. On the base of SEM observation, the procedure of the formation of apatite on C/C composite is described. We suggest that the procedure of HA deposition could be simplified to two steps, e.g. the movement of ions including Ca and P species toward C/C cathode and the growth of HA on the surface of C/C composite. In virtue of this description, the kinetics formulas of HA deposition is derived and it is found that the deposition procedure is controlled by ion diffusion in the electrolyte and the diffusion activation energy is 30.3 kJ/mol.