The invention discloses a high quality perovskite thin film, a solar cell and a preparation method thereof. The method uses solvent soaking to assist crystallization, and uses a mixed steam of water and organic solvents to assist baking so as to prepare the high quality organic and inorganic composite perovskite thin film. The high quality perovskite thin film prepared by the method is good in crystallinity, and uniform, smooth and with no defects and holes in a wide range. The preparation method provided by the invention is simple in operation, strong in operability and controllability, and very suitable for preparation of large area perovskite thin film solar cell, therefore, the preparation method has a great potential application value in the field of solar cell or other scientific fields.