The main purpose of this work is to co-deposit nano-SiO2 particles into the copper coatings on carbon fiber reinforced epoxy (C/EP) composite surface by electrodeposition method in order to improve the micro hardness of coatings. C/EP composites are copper plated with sulfuric acid based solution, and the effects of nano-SiO2 and C6H12O6 in the electrolyte contents on the copper coatings are investigated. It is found that crystalline grains of coatings are markedly refined by nano-SiO2 in the acidic sulfate copper plating bath and the ceramic particles cause an increase in hardness of coatings though nano-SiO2 results in a decline of deposition rate and a decrease in electrical conductivity of electroplating layers. Otherwise, C6H12O6 in the plating bath is indispensable to the layer formation even though nano-SiO2 added. These results demonstrate that the hardness of coatings will be increased with appropriate contents of co-deposited SiO2 and C6H12O6 in the plating bath. (C) 2009 Published by Elsevier B. V.