This article presents a comprehensive analysis of the dispersion characteristics of virtually imaged phased array (VIPA) based on the principle of paraxial dispersion. It proposes a calculation equation for the Brillouin shift specifically designed for a single-stage VIPA-based Brillouin scattering measurement system. To capture Brillouin scattering images of water and anhydrous glycerol, a Brillouin scattering measurement system is constructed. The Brillouin shift of both substances is calculated using the proposed method in this article as well as the methods proposed by Giuseppe Antonacci and Pei-Jun Wu. The comparison of the three calculation results with the theoretical values confirms the accuracy and reliability of the proposed method. Moreover, this study addresses practical challenges in Brillouin image processing and introduces a precise method for extracting Brillouin spectra from the images. Additionally, a spectral calibration program is developed using MATLAB, guaranteeing accurate spectral extraction while greatly streamlining the spectral processing workflow.