In general, for the WPT (Wireless Power Transfer) system, as the mutual inductance and load resistance are calculated according to the measured data of both the transmitter and receiver, the wireless communication modules are needed to share data. A method for estimating mutual inductance and load resistance without wireless communication is proposed, based on the fundamental and third harmonic components. The circuit is decomposed with respect to the frequencies, by which the mathematic model is established. The fundamental and harmonic components of the output voltage and current of a high-frequency inverter are found by FFT (Fast Fourier Transform). The experimental WPT system with a SiC power MOSFET is designed, and the effectiveness of the proposed method is verified by the simulation and experiment results. Additional hardware and frequency scanning operation are not needed because of the use of the harmonic components.Generally, the Magnetic Resonance Coupling Wireless Power Transfer (MRC-WPT) system consists of three parts, namely a high-frequency power supply, a coil set (transmitting and receiving coil; some systems may have more than one intermediate coil in the coil set), and a receiver circuit. The coupling coefficient (or mutual inductance) between the coils and the load resistance are directly related to the performance of the system (for example, efficiency, transfer power, etc.) [29][30][31].The measured data of the load voltage and/or current of the receiver are transferred to the transmitter through wireless communication, and these data take part in realizing the constant current, constant voltage, or constant power of the load.In [32,33], the methods for keeping the constant voltage of the load were represented using the communication module. In [34], the method for maintaining the constant voltage and the current of the load was realized using the communication module. It was implied that the relative position between the transmitter and the receiver moved infrequently, and the internal resistance of the battery was very slowly changed when charging the battery of an electric vehicle, then the concept of the weak communication was defined. In spite of the communication environment being unstable, the load resistance and mutual inductance could be derived, but the communication function was not completely removed from the system. Due to the use of the wireless communication module, the power consumption may be increased, and the normal communication function cannot be performed in some severe situations. It is more unacceptable that if only one of the communication modules among the transmitter and the receiver is damaged, the whole WPT system cannot be operated. In [35], a method in which power and data were transferred at the same time through only one coil was proposed.If the load voltage and/or current can be estimated without any measured data of the receiver, the difficulties mentioned above do not need to be considered; while, if the inductance and capacitance of the receiver (L 2 , C ...