The present invention is directed to a de-spreading method for a noncoherent receiver including: obtaining an output signal from a matched filter of a noncoherent receiver, which is PSK modulated and is at least two times upsampled; performing a noncoherent demodulation step including performing a differential operation on an in-phase and quadrature-phase components of the output signal of the matched filter to obtain a demodulated signal; and performing a de-spreading step on the demodulated signal with a PN table corresponding to the demodulated signal to obtain the de-spreaded data, wherein the PN table corresponding to the demodulated data contains chips which are either logic 1 or logic −1. A noncoherent receiver is also provided.