Abstract: The invention provides a method for preparing doped nano-silicon by using doped gas, so that the size and performance of the nano-silicon material can be accurately controlled, and the large-scale preparation of the doped nano-silicon material can be realized at the same time. In the process of synthesis, the invention carries out in-situ controllable element doping on the nano-silicon, improves the conductivity and light response performance of the nano-silicon material, and applies the prepared doped nano-silicon as a photoelectrode material in the field of optical supercapacitors. First of all, the doped nano-silicon material was obtained by using the equipment of producing metal nano-powder with automatic control DC arc in the mixed atmosphere of hydrogen, inert gas and gas containing doped elements, using tungsten electrode as arc cathode and silicon block as arc anode, starting arc to evaporate the raw material of silicon block, and on the basis of in-situ preparation, the doped nano-silicon material was obtained at one time. The invention has rich raw material sources, simple preparation process and large-scale preparation. The product is environmentally friendly and pollution-free, and the structure is novel. The addition of doping elements improves the photoelectric characteristics of nano-silicon structure.