The brightness reversion of the white cardboard for tobacco printing (coated tobacco board) affects the consistency of the appearance of tobacco packages. Exploring the mechanism of the brightness reversion of coated tobacco board is a key issue to solve this phenomenon. Based on the aging experiment of different types of coated tobacco board, the changes in brightness, Lab value, chemical composition and functional groups of coated tobacco board before and after aging are analyzed qualitatively and quantitatively. Methods such as whiteness tester, Fourier transform infrared reflection (FT-IR), Scanning electron microscope and energy dispersive analysis of X-ray (SEM-EDXA), energy spectroscopy (XPS) are applied. Lignin is the main factor causing the brightness reversion of coated tobacco board, and the brightness reversion can be evaluated by the carbonyl content. In this work, the mechanism of brightness reversion of coated tobacco board was clarified, which provided useful theoretical support for solving this phenomenon.