This work aims to prepare an irreversible thermochromic coating with a variety of thermochromic behaviors in the range of 120 to 200 ℃, which can be used to quickly troubleshoot and accurately recorded the overheating fault location of power grid equipment. First, two cobalt-based thermochromic materials were prepared from cobalt carbonate and cobalt chloride in water by a simple solution method. The thermochromism coatings were obtained by high speeded grinding for 4~5 h with silicone WB300 resin as film forming material, two kinds of self-made materials and ammonium metavanadate as chromic pigment. The structure and microstructure of the material were characterized by XPS, XRD, FT-IR and SEM. The thermal color of the coating was observed by heating in a drying oven in the range of 120 to 200 ℃, and the color difference meter and image processing software were used for data processing of the color change points. Combined with XRD, XPS, FT-IR and TG characterization, it is proved that the dark green potassium tris oxalate cobalt oxalate changed to pink cobalt oxalate at 130 ℃, and the rose red ammonium cobalt phosphate changed to dark blue cobaltous hydrophosphate at 180 ℃. The adhesion of the coating reaching the first level, the impact resistance is 50 cm, no coating rupture appearing, and the hardness is 2H. There are 5~6 discoloration points at 120 to 200 ℃, and the color-temperature function model is established. Two cobalt-based thermochromic materials are made successfully. The polychromic temperature indicator coating with obvious color difference was successfully prepared by color matching. The basic physical properties all met the national standard of conventional coating. The coating will turn black when heated to 200 ℃ and will not change.