The invention provides a spectroscopic ellipsometry real-time monitoring preparation method of nano-silicon thin film solar cells. The preparation method comprises seven major steps. Anisotropic etching is performed on a single crystal silicon wafer by use of a chemical method to form a pyramid-shaped texturized silicon wafer substrate; an intrinsic nano-silicon film having the crystalline content within the range of 50+/-5% and the crystalline peaks within the range of 502-518cm-1 is prepared by use of a plasma enhanced chemical vapor deposition method, and a type N nano-silicon film can be prepared by doping PH3 and the like in the deposition process, and a type P nano-silicon film Can be prepared by doping b2h5; in the deposition process of the nano-silicon film, the preparation method of monitoring the growth process of the film in real time by use of spectroscopic ellipsometry is adopted, which is the core technology of the application; back electrodes, upper electrodes and transparent electrodes of nano-silicon thin film solar cells are prepared by use of a thermal evaporation method or a magnetron sputtering. The nano-silicon thin film solar cells having repeatability and high photoelectric conversion efficiency can be prepared by use of the spectroscopic ellipsometry real-time monitoring preparation method.