The invention relates to a hot-forging lubricating agent and a preparation method and application thereof, and belongs to the technical field of forging forming. The hot-forging lubricating agent is prepared from nano MoS2, hexagonal BN, methyl trinitrate, water glass, nano MgO and water. All the components are fully mixed and then sprayed on the surface of a mold and the surface of a blank before use. According to the hot-forging lubricating agent and the preparation method and application thereof, good lubricating performance, demoulding performance, cooling and heat insulating performance, high-temperature wetting performance (film-forming performance), suspension dispersion performance and jetting performance are guaranteed within the forging temperature range, and the hot-forging lubricating agent further has the lubricating performance, particular the high-temperature lubricating performance equivalent to that of a graphite type lubricating agent and is particularly suitable for metal hot die forging, particularly hot die forging of large aluminum parts; the hot-forging lubricating agent does not react with aluminum alloy and is a pollution-free water-based lubricating agent and is not a graphite type lubricating agent. When the lubricating agent is used for isothermal die forging of high-strength aluminum alloy, a lubricating and protecting film is formed on the surface of a die forging part, and the hot-forging lubricating agent is particularly suitable for forming lubricating of large-scale complicated-structure high-strength aluminum alloy die forging parts for space flight and aviation and suitable for industrialized application.