In recent years, wireless power transfer (WPT) technology has developed rapidly. Facing the demands of multi-load and multi-frequency compatibility, the development of multi-frequency magnetically coupled resonant wireless power transfer (MCR-WPT) has attracted increasing attention. This paper proposes a coplanar dual-frequency multi-load MCR-WPT system based on the principle of magnetic coupling resonance. In this system, the transmitter coil and the relay coil are placed coplanar, and the receiver coil is placed on the charging platform formed by the relay coil. The transmitter coil and the relay coil are connected through ferrite. Compared with the traditional coaxial placement of coils, the coplanar arrangement of coils has advantages such as low profile, high space utilization, and strong flexibility. Through the design of the system coupling mechanism and the analysis of the equivalent circuit model, the transmission characteristics of the system are studied and analyzed. Finally, an experimental platform is built to verify the system. The experimental results show that the system has dual-frequency transmission characteristics and can achieve the transfer of energy at two different target frequencies. It is insensitive to the position offset of the load receiving end, demonstrating good anti-offset characteristics, as well as the load-independent constant voltage output characteristics.