The present invention provides a multi-carrier separation method and a multi-carrier separation device. The method implements digital mixing by a cycle shift of a frequency domain, implements linear block convolution by a cycle convolution based on Fast Fourier Transform (FFT), further implements a low pass filter by multiplication of the frequency domain and low frequency window; at the same time, the method also employs other various means for reducing unit sampling point calculation amount, which greatly reduces the multi-carrier separated calculation amount, saves the hardware source and reduces the hardware cost.