The invention discloses a signal modulation method capable of reducing the peak to average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal, and relates to the technical field of OFDM signal transmission. The signal modulation method comprises the following steps of: 1, dividing N sub-carriers into L sideband information sub-carriers and N-L useful sub-carriers, wherein L is less than N; and 2, modulating signals to be transmitted onto the useful sub-carriers, extracting peak clipping signals C according to the parts, exceeding a target peak value, of the modulated signals, modulating the peak clipping signals C onto the useful sub-carriers, and modulating positions, amplitudes and phases exceeding a target peak value point onto the sideband information sub-carriers to form transmitted signals xtr. By the method, peak value points of the original signals can be accurately eliminated; and compared with the conventional method, the method is easier to implement.