The thickness of glass ,as a crucial index in industrial production ,has become a research hotspot for its rapid measurement. This paper proposes the use of laser scanning interferometry ,interpolating the sampled signals ,correcting the beat frequency nonlinearity ,and then obtaining distance information through spectral estimation. When measuring thinner glass ,the FFT algorithm is affected by the fence effect and spectral interference ,making it difficult to distinguish the frequency of the front and back surfaces of the glass in the spectrum. To address this issue ,this pa- per employs the Root-MUSIC algorithm to process the signal. Experimental results show that when the FFT algorithm fails to resolve adjacent target frequencies ,the Root-MUSIC algorithm can effectively distinguish them. The computa- tional efficiency is also much higher than the MUSIC algorithm ,and the accuracy can reach 0. 05 μm ,providing a so- lution for the problem of glass thickness measurement.