A back surface field aluminum paste for point contacts of efficient bifacial crystalline silicon solar cells and its preparation method is disclosed. The aluminum paste, which is used to cover the notched area in the back surface of a bifacial passivated solar cell, and not to cover the entire area covered by a back surface passivation film, comprises 85-95 parts by weight of aluminum powder, 10-15 parts by weight of organic carrier and 0.1-6 parts by weight of inorganic binder. The organic carrier includes thickening agent, thixotropic agent, dispersing agent and solvent. Sintered aluminum gate lines have a certain height to width ratio.