An energy harvesting power supply based on AC electric field induction is introduced, which is used for power supply of online monitoring devices for transmission lines. However, the output power of this type of power supply is relatively low, which cannot meet the electricity demand of online monitoring devices. Therefore, based on theoretical analysis, a coaxial dual column inductive electrode structure is designed in the article to improve the output power of the power supply. A simulation model is established using COMSOL Multiphysics software and electromagnetic field simulation analysis is conducted. The simulation results show that the designed inductive electrode can generate an induced current of over 3.35 mA at a voltage level of 10 kV. To verify the accuracy of the simulation results, an experimental verification is conducted using a self built testing platform in the laboratory, and the experimental results are compared with the simulation results. The experimental results show that when the value of load resistance is higher than 5 kΩ, an energy harvesting power supply can output continuous power exceeding 630 mW, which is basically consistent with the simulation results. Through the research in the article, the problem of low output power of electric field induction energy harvesting power supply has been successfully solved, and a new design concept and technical solution of energy harvesting circuit has been proposed.