The present invention discloses a speech/audio signal processing method and apparatus. In an embodiment, the speech/audio signal processing method includes: when a speech/audio signal switches bandwidth, obtaining an initial high frequency signal corresponding to a current frame of speech/audio signal; obtaining a time-domain global gain parameter of the initial high frequency signal; performing weighting processing on an energy ratio and the time-domain global gain parameter, and using an obtained weighted value as a predicted global gain parameter, where the energy ratio is a ratio between energy of a historical frame of high frequency time-domain signal and energy of a current frame of initial high frequency signal; correcting the initial high frequency signal by using the predicted global gain parameter, to obtain a corrected high frequency time-domain signal; and synthesizing a current frame of narrow frequency time-domain signal and the corrected high frequency time-domain signal and outputting the synthesized signal.