This paper proposes a multi-frequency channel wireless charging system with metal foreign object detection capability. The system fully utilizes the rich harmonic components in the inverter square wave, employing the fundamental and third harmonic components for constant-voltage charging of devices with different voltage levels, while the fifth harmonic component is connected to a detection coil array for metal foreign object detection. Each frequency channel in the system is isolated from the others and can operate independently. The paper establishes an equivalent circuit model for the multi-frequency channels, analyzes the output characteristics of the power transmission channels and the detection principle of the metal foreign object detection circuit. Circuit simulations verify the directional reception of the target frequency components in each channel. An experimental platform was built to test the constant-voltage output characteristics of the energy transmission channels and the detection performance of the metal foreign object detection circuit. The results confirm that the frequency channels do not interfere with each other.