Abstract: It takes a long time and high cost to repair the damaged valve sealing from power plant to factory, and it requires destructive separation of the valve, which may bring safety hazards. In recent years, online hardfacing repair technology for valve sealing has received increasing attention. In the paper, it reviews the status of online hardfacing repair technology for valve sealing in power plants. It summarizes the failure forms of valve sealing in power plants, process and special requirements for online hardfacing repair of valve sealing in power plants, and focuses on the research and engineering practice progress in hardfacing materials, online hardfacing repair methods and equipment, and online machining and grinding after hardfacing. Further research works need to carry out as follows. It needs to develop flux cored welding wires of Stellite alloy. It needs to develop nickel based and iron based hardfacing alloy wires with high hardness, high wear resistance and crack resistance for valve sealing. It needs to develop low splash automatic MIG/MAG hardfacing process for valve sealing. It needs to develop specialized equipment for online hardfacing repair of valve sealing in power plant. It needs to develop online machining equipment highly integrated with specialized equipment for online hardfacing repair.