A phase spread frequency sampling method is proposed. This method can be used to correct the nonlinearity in the beat frequency of a measurement signal. The proposed method expands the phase of the auxiliary interference beat signal, thereby satisfying the Nyquist sampling theorem, correcting the nonlinearity in the beat frequency of the measured signal, and solving the problem of limited range. The conditions over which the frequency sampling method can be applied are expanded. The measurement range is flexibly expanded by performing multiple phase expansions.