To achieve fast and accurate measurement of the luminance of flat-panel displays, an imaging spectrometer based on linear variable filters was used for theoretical analysis and experimental validation. The principle, structure, and application characteristics of the imaging spectrometer with linear variable filters as the core was discussed and a mathematical conversion model of light source luminance-output grayscale value was established. A spectral calibration and radiation calibration device based on an LED integrating sphere light source and a spectroradiometer was developed, and the spectral cube data of the target was obtained, along with the absolute spectral power distribution curve of each point. The results show that the relative display error is less than 3%, meeting the first-level measurement accuracy requirement of the national standard for luminance measurement. The rapid and accurate measurement of surfece light source luminance is realized. This study provides a favorable reference for optimizing the quality control and product adjustment of the display industry.