The invention relates to a heat-insulating fireproof interface agent for a polystyrene heat-insulating plate. The heat-insulating fireproof interface agent comprises 20-25 parts of silicate cement, 2-5 parts of coal ash, 2-3 parts of bauxite cement, 0.4-0.6 parts of plasticizer, 0.5-1.0 part of water reducer, 0.1-0.2 parts of ethylene oxide, 0.1-0.2 parts of tartaric acids, 0.1-0.2 parts of calcium stearate, 0.05-0.1 parts of polypropylene cellulose, 5-8 parts of vinyl acetate / ethylene polymer, 4-6 parts of 200 mesh sand, 4-6 parts of 400 mesh sand, 5-8 parts of 800 mesh coarse whiting, 5-8 parts of kaolin, 8-10 parts of aluminum oxide, 5-10 parts of magnesium hydroxide, 3-5 parts of zinc borate, 8-13.5 parts of ammonium polyphosphate, 0.2-0.5 parts of 1-2mm basalt fibers and 8.5-15 parts of expanded perlite. The heat-insulating fireproof interface agent for the polystyrene heat-insulating plate has the advantages of simple construction, excellent fireproof heat-insulating effect, excellent cracking resistance and high bonding strength with the polystyrene heat-insulating plate.