The invention discloses a preparation method of perovskite single crystals. The preparation method comprises the following steps: taking and mixing first halide and second halide, stirring and dissolving with a polar solvent, and preparing a perovskite solution, wherein the mass ratio of the first halide to the second halide to the polar solvent requires that the perovskite solution is supersaturated; performing filtering treatment on the perovskite solution; putting the perovskite solution after filtering treatment in a hydrophobic container, heating and separating out the perovskite single crystals. In the preparation method disclosed by the invention, a hydrophobic material is selected as a growth container for the perovskite single crystals; due to the hydrophobicity of the wall of the hydrophobic container, the number of crystal nucleus growing on the wall of the hydrophobic container is sharply reduced, the number of the crystals grown is relatively reduced, the grown crystals are larger within unit time, the quantity of broken crystals is reduced, the utilization rate of the solution is improved, and the crystal quality is significantly improved.