Advanced thermal spraying technology represented by supersonic flame spraying, high-power plasma spraying, etc., has become the key equipment and technology that components achieve high temperature wear resistance, corrosion resistance, anti-nodulation, heat insulation and other functions under harsh service environments. The basic principles and coating characteristics of different thermal spraying technologies are outlined, furthermore, the research status and application of thermal spray technology in severe service environments regarding metallurgical key equipment (such as continuous casting crystallizer copper plates, hot-dip galvanized aluminum pot components and high temperature furnace rollers) are discussed in detail. For molten metal, inside and outside the large temperature difference between the environment of continuous casting crystallizer copper plate surface repair and strengthening, thermal spray technology has the potential to replace the traditional plating technology, the prepared thermal spray layer has excellent thermal conductivity, corrosion resistance, wear resistance, etc., of which WC-Co series and NiCr-Cr3C2 series are the two most representative coating materials. For the protection of hot-dip galvanized and aluminized line zinc pot with a service environment of molten metal, thermal spraying technology can replace some other coating technologies and boronizing treatments by preparing high-quality coatings with high bonding strength, which can effectively improve the performance of corrosion resistance to liquid zinc or aluminum. The coating materials mainly include ceramic and cermet materials. For the protection of high temperature furnace roller with service environment of high load and high temperature, WC-Co is the commonly used coating in the low-temperature section, Cr3C2-NiCr in the medium-temperature section, ceramic, cermet, and cermet/rare earth oxide in the high-temperature section. Finally, the future development of thermal spraying technology in the field of metallurgy will be prospected, in order to further promote the deep and wide applications of thermal spraying technology in the metallurgical field.