The invention relates to Janus nano-particles and a preparation method thereof, and belongs to the field of dental restoration. A nanoscale Janus material on the hydrophobic side of which polymerizable unsaturated double bonds exist is prepared by regulating the factors of different chemical composition divisions of the Janus nanometer composite material, such as division area, chemical composition, particle size distribution, quantity of double bond groups and the like. Groups with high compatibility with oil and water phases are respectively introduced onto the surfaces of the nano-particles, and a 'dynamic' Janus structure is formed on an oil-water interface so as to obtain the nano-particles arranged in a one-layer manner. Furthermore, due to chemical reaction modification in a selected area, the Janus nano-particles with a 'stable' structure are obtained. The nano-particles are endowed with temporary Janus amphiphilic properties on an emulsion interface by utilizing dynamic bonds and thus are arranged on the emulsion interface in a one-layer manner so as to obtain stable Pickering emulsion. Zoning modification can be further performed after zoning protection, and the Janus nano-particles are prepared. The nano-particles have high adsorption energy on the interface, are less prone to rotation and can be distributed on the emulsion interface in a one-layer manner.