The invention relates to a silicon solar cell and a preparation method thereof. The method comprises the following steps: preparation of a silicon nanowire array on the upper surface of an N-type monocrystalline silicon piece, preparation of a first interface modification layer, and preparation of a second interface modification layer and first PEDOT (poly(3,4-ethylenedioxythiophene)): preparationof a PSS (poly(sodium-p-styrenesulfonate)) layer and second PEDOT: thermal evaporation of metal copper on the whole surface of the PSS layer, preparation of an obverse gate electrode and preparationof a reverse electrode. By improving the structure and preparation process of a photovoltaic cell with a silicon-based core shell structure, the photoelectric conversion efficiency of the silicon solar cell is effectively improved.