A wireless charging circuit coupled to an oscillation unit. The wireless charging circuit includes a balun unit, a higher-order filter unit and a differential unit. The balun unit is coupled to the oscillation unit. The higher-order filter unit is coupled to the balun unit. The differential unit is coupled to the higher-order filter unit. The differential unit is coupled to a transmission coil. The oscillation unit issues a differential signal to the balun unit, and then the balun unit converts the differential signal into a converted signal to be transmitted to the higher-order filter unit. The higher-order filter unit filters the converted signal to output a filtered signal to the differential unit. The differential unit converts the filtered signal into a differential output signal to be outputted by the transmission coil.