The invention relates to signal transmitting engineering. The use of the inventive method in systems for transmitting and receiving quadrature amplitude-modulation signals (QAM) exhibiting a low carrier frequency synchronization threshold makes it possible to decrease a demodulation threshold by means of said low carrier frequency synchronization threshold. The result is attainable by supplementing a burst of M m-level sensitive QAM symbols by predetermined symbols, one part of which remains constant form one burst to another and the other part is periodically invertible in certain bursts, thereby the QAM signal components corresponding to the additional predetermined symbols (whose frequencies are known) are extracted on a receiving side. The inversion frequency is determined according to said components, thereby making it possible to eliminate the ambiguity of the receiving frequency synchronization control and to approach the Shannon's threshold.