The invention discloses a preparation method for a Te/PbTe heterojunction nanometer thin film. PbTe is deposited on the surface of an electrode by adopting an electro-deposition method to form a carrier thin film; the electrode is immersed into 0.1mol/L of NaNO<3> solution; then the electrode is oxidized by adopting an electrochemical method; and finally, the electrode is taken out, and the Te/PbTe heterojunction nanometer thin film is formed on the electrode through oxidization. The preparation is quite efficient and simple; and compared with a PbTe nanometer thin film, the prepared Te/PbTe heterojunction nanometer thin film is higher in photoelectric conversion efficiency and low in cost, so that large-scale popularization and production can be realized easily.