Transmission Line Parameter Test System is of an integrated structure, with a built-in variable frequency power supply module and a variable frequency voltage regulating output power supply. The frequency can be changed to 45Hz and 55Hz. Digital filtering technology is adopted to avoid the interference of power frequency electric field to the test and fundamentally solve the difficult problem of accurate measurement under strong electric field interference. At the same time, it is applicable to the occasions where the generator is used for power supply detection after all power outages.