The invention belongs to the field of micro-nano manufacturing related equipment, and discloses an atomic layer deposition thin film preparation equipment of a normal-pressure lower curved face substrate. The equipment comprises a spray head module and a hydraulic transmission module which is correspondingly equipped, wherein the spray head module is used for carrying out atomic layer deposition on the substrate and has a space isolation function, and an air floatation area on the periphery can help a spray head to change the direction when the spray head passes through a curved face to achieve the effect of curved face deposition; the hydraulic transmission module acquires information of the rotating angle of the spray head in real time through a rotary valve, and by changing the relativeconnection position of an oil inlet and an oil outlet, the spray head can ascend or descend or keep unchanged overall. By means of the method, the atomic layer deposition thin film preparation equipment with an open type and a self-adjusting function can be obtained, various curved face deposition operations can be performed at normal temperature and normal pressure by the equipment, the angle ofthe spray head can be quickly changed and the spray head perform lifting motion according to the curvature of the curve face, so that the working efficiency and applicability can be remarkably improved compared with the prior equipment.