Janus materials with anisotropy shapes and chemical compositions, including Janus particles, Janus nanosheets, and Janus membranes, have a great significance in the development of new functional materials and expansion of the properties and applications of materials. This review summarizes recent works on Janus materials of preparation, application, assembly, and calculation. First, we briefly sort out the methods of preparing Janus particles and discuss the factors influencing the structure, shape, and size of Janus particles, pointing out their advantages and the direction of improvement. Then, we introduce in detail the applications field from a single Janus particle, assembly of Janus particles, 2D Janus nanosheet, and Janus membrane. We summarize the recent research on the self-assembly of Janus particles and point out the role of the combination of computational simulation and experiment in the research of Janus material. Finally, the research process of Janus materials is reviewed, and the development tendencies of Janus materials and the problems to be solved are summarized.