In the mountainous area of Guizhou Province

it is difficult to measure the power frequency grounding resistance of transmission line poles and towers by the traditional three electrode method. This paper compares several methods of measuring tower grounding resistance

including three electrode method

clamp meter method and looping method

and compares the difference of grounding resistance measured under different grounding resistance measurement methods

analyzes the error reason from actual measurement. Four towers in 220 k V Taibai line are measured by three electrode method and loop method to compare their difference. The requirements of using loop method to measure grounding resistance are specified and it has important guiding significance for measuring grounding resistance in practical work.