Abstract: The basic working process and special requirements for traveling wave tube filament for power supply are introduced and the characteristics of filament are also analyzed. The particularity and difficulty of filament power supply design are thoroughly analyzed. Based on the Topswitch series control chip performance and characteristics, the main circuit of the flyback converter of the filament power supply is designed. According to the start-up characteristics of the filament and the basic requirements of stability, a high precision feedback circuit and a current limiting circuit are designed. The feasibility of the hardware implementation is verified through experimental works with a prototype. The simulation experiment, laboratory and harsh environment test results show that the main circuit, feedback circuit and current limiting circuit can well meet the traveling wave tube filament requirements.