The invention provides a high temperature protective coating. The coating reacts with a preferential slightly produced oxide layer at a temperature of between 800 and 1,350 DEG C to generate a denatured compact oxide layer, thereby preventing the further mutual infiltration of iron and oxide through the self compactness of the denatured oxide layer. The protective agent powder mainly comprises the following components in percentage by mass: 30 to 70 percent of TiO2, 14 to 28 percent of Al2O3, 0.5 to 1 percent of Y2O3, 0.5 to 1 percent of ZrO2, 0.5 to 1 percent of HfO2, 4 to 20 percent of ZnO, 4 to 10 percent of Fe2O3, 6 to 12 percent of SiO2, 0 to 2 percent of NaO, and 0 to 2 percent of K2O. When the powder is put into use, the powder and water are mixed according to the proportion of 1:1 to prepare slurry; the binder water glass which is 5 to 15 percent of the mass of the slurry is added; and the dispersant carboxymethyl cellulose which is 0.5 to 1.5 percent of the total mass of the slurry is added. The lab experiments and medium-scale experiments in steel enterprises shows that: the protective agent is suitable for most carbon steel; the protective agent has good floatability and no impact on heating; and the modified iron oxide scale has very good stripping performance, the metal surface has good quality, and the decarbonization is effectively prevented.