The invention provides a wideband spectrum sensing method of a single-channel structure based modulated wideband converter in order to solve problems that the structure of an MWC (Modulated Wideband Converter) system is complex and that the number of channels is uncertain brought about by the uncertain number of signals, and belongs to the field of information and communication technologies. The wideband spectrum sensing method comprises the steps of S1, modulating an original signal by using a modulation function to obtain a spectrum of a modulated signal, wherein the original signal is a multi-band signal, namely, a wireless signal received by the MWC system in a natural environment; S2, extracting the spectrum of the modulated signal by combining frequency shift characteristics of Fourier transform according to characteristics of single-channel signal spectrum translation, and enabling the modulated signal to be equivalent to a signal of multiple sampling channels, that is, obtaining an equivalent multi-channel signal; and S3, performing under-Nyquist sampling on the multi-channel signal obtained in the step S2, and processing the original signal with sparse features to obtain spectrum position information of the original signal, thereby finding an idle spectrum, and completing wideband spectrum sensing.