A method and device for complex carrier demodulation are provided by the disclosure. The method includes: demodulating modulated signals using complex signals e−iωt or eiωt as carrier signals to obtain complex carrier demodulation signals. Therefore, the utilization rate of spectrums is improved. With the method for complex carrier demodulation provided by the disclosure, the left and right frequency spectrum resources are fully utilized, the loss of signal energy is little, thereby the channel capacity is improved greatly.