The invention discloses a method for reducing a peak-to-average power ratio of multiple input multiple output (MIMO) - orthogonal frequency division multiplexing (OFDM) signal for space-frequency coding. On a transmitter end, data is coded, interlaced, modulated and alamounti space-frequency coded to obtain a group of frequency-domain sequence, the group of frequency-domain sequence is grouped, so multiple groups of candidate time-domain signals are obtained by selecting appropriate parameters, and a group of time-domain signals with the minimum peak-to-average power ratio (PAPR) is selected to be transmitted. On the end of a receiver, after the operation of a received signal such as fast fourier transformation (FFT), estimation of a channel, space-frequency coding and the like, a frequency-domain signal which is superimposed by the channel noise is obtained, and the hard decision is performed on the frequency-domain signal to obtain a nose-free frequency-domain signal. The signal is restored according to all possible combination ways to obtain candidate data, and only the data which is restored by adopting a correct restoring way conforms to the original modulation constellation.The method can effectively reduce the peak-to-average power ratio of the MIMO-OFDM signal, is free from transmitting the side information, improves the frequency band utilization rate of the system, and can be applied to different communication systems based on the space-frequency coding-based MIMO-OFDM technology.