The invention relates to the technical field of rock plate back coating material processing, and particularly discloses a two-component back coating material for a rock plate and a preparation method thereof, and the two-component back coating material is prepared from a powder mixture and a liquid mixture; the powder mixture is mainly prepared from the following raw materials: quartz sand, ordinary Portland cement, cement-based capillary crystalline master batch, hydroxyethyl cellulose, dispersible latex powder, diatomite, bamboo charcoal powder and aluminum oxide; the liquid mixture is mainly prepared from the following raw materials: a water-based polymer emulsion, 2, 2, 4-trimethyl-1, 3-pentanediol monoisobutyrate, sodium citrate, a penetrating agent, a wetting agent and a silane coupling agent. According to the two-component back coating material, the synergistic effect of the raw materials is utilized, so that the two-component back coating material has relatively high bonding strength, thermal aging resistance and freeze-thaw resistance, shows good bonding stability and sound absorption and noise reduction effects, meets the market requirements and expands the application range.