Abstract: For promoting the signal-to-noise ratio using the phase-inversion symmetric modulation in frequency domain, a method for computing the correlation of noise is presented and the correlation of noise in adjacent frequency bands in the case of partially and fully overlapping is researched. The existence of relevance of noise in adjacent frequency bands is authenticated, and both the relevance and its stability become stronger as the width of frequency band decreases. The correlation of noise in adjacent frequency band decreases linearly as the overlap decreases in adjacent frequency bands, which provides the guidance for further promoting the signal-noise ratio using the phase-inversion symmetric modulation and enriches the theory of communication noise.