The invention relates to method for preparing a two-dimensional atomic crystal new material by supercritical fluid. The method comprises the steps of: by taking laminated structure materials such as boron nitride (BN), molybdenum disulfide (MoS2), tungsten disulfide (WS2) as raw materials, and taking supercritical fluid (carbon dioxide CO2) as a stripping agent, successfully stripping new two-dimensional atomic crystal material for preparing BN film, MoS2 film, WS2 film and the like, wherein each film exists in a form of a single layer (monoatomic layer) and a few thin layers (a few atomic layers). The two-dimensional atomic crystal film prepared by the method has the same or similar structure with graphene, and has excellent mechanical property and transmittance property. Each film has excellent electrical, magnetic, thermal and optical performance, and has important application prospect in many fields; and by the technology of preparing the two-dimensional atomic crystal film by supercritical fluid in a stripping way, the product film has the advantages of controllable layers, excellent structure, high yield, simple process and low cost.