The present disclosure provides a method for preparing a perovskite quantum dot film by one-step crystallization, and belongs to the field of perovskite quantum dot material technology. The present disclosure uses adamantanemethylamine and hydrohalic acid as ligands, first mixes a cesium halide, a lead halide, and the ligands with a solvent to obtain a precursor solution, then deposits the precursor solution on a substrate, and then heats the substrate to obtain the CsPbX3 perovskite quantum dot film. The present disclosure uses adamantanemethylamine and hydrohalic acid as the ligands, which can quickly coat the perovskite, complex with the CsPbX3 perovskite, and directly form the perovskite quantum dot via a strong steric effect. Further, the present disclosure is simple and inexpensive, can directly obtain a high-quality perovskite quantum dot film with a thickness of more than 500 nm by one-step crystallization.