In recent years, the omnidirectional wireless power transfer technology has attracted extensive attention of domestic and foreign research institutions and institutes owing to its unique advantages such as good location robustness, high safety and reliability, and strong environmental affinity. The high-performance electromagnetic coupling system is the key link in an omnidirectional wireless power transfer system, which is important for the realization of the system's efficient energy transfer. First, the equivalent circuit model of an omnidirectional coil structure is established by using the circuit theory, and the expressions of system output voltage and output power are obtained. In addition, the control scheme for the system's excitation source is also given. Then, the charging scenarios of omnidirectional wireless power transfer are analyzed. The disadvantages of a 3D-orthogonal circular ring transmitting coil structure scheme are analyzed, and a cube transmitting coil structure scheme is proposed. Finally, the mathematical models of two magnetic coupling coil structure schemes are established, thus obtaining the relationship between mutual inductance and the position of receiving coil, charging scenario and rotation angle. The theoretical analysis is verified by simulation experiments, providing reference for the design of an electromagnetic coupling system of omnidirectional wireless power transfer.