The invention discloses a preparation method for a cooper selenide-based thermoelectric material. According to the preparation method, the electrical conductivity of a composite material obtained by the method is controlled by joint effects of content of nanocarbon fibers and content of Cu, and the nanocarbon fibers can effectively improve the electrical conductivity of the obtained composite material; the electrical conductivity of the obtained composite material is improved along with decreasing of the content of Cu; and finally, the thermoelectric performance of the material is greatly improved. The preparation method is simple and rapid, and the raw material utilization ratio is high, so that the preparation method has high industrialization prospect.