Aiming at the problems of insufficient range, high maintenance cost and insufficient inspection frequency of online monitoring equipment in transmission line inspection, this paper designs a U-type triple-coil wireless power supply system using a U-type triple-coil wireless power supply system and at the same time proposes a parameter design optimization method based on a genetic algorithm in order to realize wireless power supply of online monitoring equipment for 110 kV medium and long-distance transmission towers. On this basis, the circuit model of the U-type triple-coil wireless power transmission system is firstly established, and the relational equations between the output power, transmission efficiency and the mutual inductance of the coil, coupling coefficient, and load impedance are deduced, and then the genetic algorithm is used to search for the optimization of the parameters and obtain the optimal solution and its corresponding system parameter values. Finally, an experimental platform is built according to the simulation data, and the experimental results show that the wireless power supply system for on-line monitoring equipment of U-type triple-coil transmission towers achieves an output power of 81.19 W at an operating frequency of 380 kHz and a transmission distance of 1.2 m, which verifies that it can meet the power supply requirements of on-line monitoring equipment.