A preparation method for a local back surface field of a crystalline silicon solar cell comprises a silicon wafer substrate, a back surface passivating film layer is arranged on the back surface of a silicon wafer, the back surface passivating film layer is partially eliminated, and the silicon wafer substrate is exposed. Through a secondary depositing method, aluminum layers are partially deposited on the area, where the back surface passivating film layer is eliminated, of the crystalline silicon solar cell, the local back surface field is formed through a high-temperature sintering method, and then the aluminum layers are completely or partially deposited on the back surface, and a back surface metal electrode is formed at low temperature. Due to the fact that at the first time, the aluminum layers are deposited on the area where the back surface passivating film layer is eliminated, holes between aluminum and silicon are eliminated in the high-temperature process, then the independent aluminum layers deposited at the first time are connected together through a complete covering or a partial covering method, and the back surface electrode is formed. The preparation method for the local back surface field of the crystalline silicon solar cell is capable of effectively eliminating the holes in the local back surface field of the crystalline silicon solar cell, and improves the photoelectric conversion efficiency of the cell.