In order to solve the charging problem of inspection robot in substation, the mathematical model of electromagnetic coupling resonant wireless transmission is presented based on the analysis of the principle of electromagnetic coupling resonant radio energy transmission. The results show that the voltage at the receiving end will show a decreasing trend when the transmission distance increases, while the large close-range coil can test stronger coupling effect and receive higher voltage. Three-dimensional coils are introduced to improve the structure of the coils. The receiving end contains 3 orthogonal coils and corresponding capacitors, and the mechanical rotation occurs in the alternating electromagnetic field. Therefore, there will be a coil and the transmitting end in the state of the strongest coupling at any angle, which can output the maximum power for the load.