The invention relates to a method and a device for detecting the resonant current at the transmitting end of a wireless charging system. The method includes the following steps: collecting the currentsignals in a precious cycle, and getting the signal cycle T; calculating the time t(phi) corresponding to a to-be-detected phase in the precious cycle, and adding the signal cycle T to t(phi) to getthe time t'(phi) corresponding to the to-be-detected phase in a current cycle; and collecting a current signal at the time t'(phi), and getting the current value of the to-be-detected phase in the current cycle. The method and the device are easy to implement, have high real-time performance, and can quickly lock the frequency, amplitude and effective value of the current high-frequency resonant current and control and protect the wireless charging system.