1. A method of collecting a signal with a sampling frequency lower than a Nyquist frequency, comprising: determining, by a data transmitting end, a sparsity k of an original input signal x, calculating a number M of compressive sampling operations according to the sparsity k, sampling the original input signal x with a frequency f NYQ /M using M channels respectively, wherein f NYQ is the Nyquist frequency of the original input signal x, integrating sampling values of each channel to obtain M measurement values y, and then transmitting the M measurement values y to a data receiving end; and restoring, by the data receiving end, the received M measurement values y to a sparse representation of the original input signal x using an orthogonal matching pursuit algorithm, and then obtaining the original input signal x by performing an inverse transformation on the sparse representation.