The performance of tower grounding electrode determines whether the transmission line can operate safely and steadily, so it is necessary to detect the status of tower grounding electrode. Firstly, the frequency response curves of grounding impedance at different frequencies are obtained by simulation. Then, we find out the common influence rule of length on grounding impedance, Finally, the rule is verified by experiment. It is found that the grounding electrode length has a great influence on the impedance modulus when the frequency is low. When the frequency increases to a certain extent, the impedance modulus of the grounding electrode with different length is gradually the same and the impedance angle is different. However, with the further increase of the frequency, the impedance modulus and the impedance angle of the grounding electrode with different length are the same. It is found that the length of grounding electrode can be detected by multiplying the modulus. Therefore, it is feasible to detect the length of grounding pole by frequency response characteristics