The invention provides a CdTe battery back electrode which comprises a back electrode buffer material and a C/Cu composite material. The C/Cu composite material is formed by nanometer copper particles and a carbon layer which coats the surface of the nanometer copper particles. According to the CdTe battery back electrode, a carbon coating copper composite material is added into the back electrode buffer material for replacing Cu. The carbon coating structure can effectively prevent an environment influence to the coated nanometer Cu particles, thereby supplying a relatively stable environment to the Cu particles. Furthermore the carbon coating copper composite material is doped into the back electrode buffer material. The coating layer is similar with a used body material slurry component, and relatively high compatibility can be realized. The Cu particle which is coated can react with a rich-Te layer for generating CuxTe for supplying a Cu material, and the generated the CuxTe can effectively improve battery performance. Furthermore because of coating by the carbon layer, front diffusion caused by Cu concentration difference is remarkably reduced from pure Cu, thereby effectively controlling Cu diffusion and realizing long-term stability of the battery.