The invention provides a signal generating method, a frequency offset detecting method and a frequency offset detecting device wherein the signal generating method comprises the steps of acquiring a first pseudo random PN sequence which is generated by a shift register and a frequency domain orthogonal frequency division multiplexing OFDM symbol that is generated by a transmitter; correspondingly adding the first PN sequence with the frequency domain (OFDM) symbol, thereby obtaining a frequency domain (OFDM) data frame; performing inverse fast Fourier transform (IFFT) on the frequency domain OFDM data frame, thereby obtaining the frame body data part of the signal frame; and constituting the data frame by the preset frame head part of the signal frame and the frame body data part of the signal frame, thereby generating a signal; wherein the preset frame head part of the signal frame comprises M preset PN sequences, and M is a positive integer which is larger than zero. Through the signal generating method, the frequency offset detecting method and the frequency offset detecting device, the frequency offset of the carrier wave can be accurately and quickly determined on condition that the frame body of the OFDM is relatively large, thereby improving system stability.