Taking energy from the ground wire is a way of supplying energy for all kinds of sensing and monitoring equipment in the power system transmission network. Therefore, the paper analyzes the principle of taking electricity of a typical overhead ground wire, establishes its equivalent parameter model, and mathematically derives the equivalent voltage and equivalent impedance of the electricity taking port. A 220kV line was selected and simulated with ATP-EMTP software. The influence of the energy load on the distribution of ground wire current is studied, and the influence law of factors including wire current, ground resistance, span range, energy load and other factors on the electricity parameters is analyzed. The results show that: limited by the induced potential and ground wire self-impedance, the ground wire current does not exceed 10A. The increase showed an increasing trend, and finally stabilized at about 27V. When the energy extraction load is 2.5Ω, the maximum energy extraction power obtained is 175.03W. These results provide a data basis for the design of subsequent energy takers.