This paper elaborates the operating principle of power supply for X-band mobile radar filament and introduces in details the 4-circuit operating voltage produced by the adjustable potentiometer on filament power board and the corresponding operating modes respectively.In addition,the signaling process of mobile radar filament power supply system is based to make a research of the fault diagnosis method for the system,in order to summarize multiple fault diagnosis processes and positioning methods related to the filament power supply system and provide intuitive information for further troubleshooting.Meanwhile,the actual working experience is combined to enumerate the fault phenomena of filament power supply and the examples of troubleshooting and maintenance,with a view to providing support and reference for the site fault handling of X-band mobile radar filament power supply.