The methods to measure power-frequency ground resistance of transmission line towers and poles have been discussed.Comparing the ground resistance measurements of different topographic position and different voltage level by using ground megger（3-pole method） and clamp meter in the site

it is found that the measuring error of clamp meter is great and the error has no regular pattern to be followed and cannot be corrected

so much attention should be paid to these points.Through comparison

the measurement of 3-pole method is regarded as the more accurate one.