Yangxindian is located in the inner courtyard of the Forbidden City in Beijing, west of the Palace of Heavenly Purity; it was built in 1537 during the reign of emperor Jiajing of Ming. The eaves of the main hall of Yangxindian are decorated with polychrome painting (caihua) of different type that denotes different ranks and was applied at different periods. In 2016, a comprehensive protection engineering program was started for Yangxindian; and based on the data obtained from the resulting field survey and textual research, this article suggests three dates for the decorative eaves painting, namely the mid- and late-Ming period, the early- and mid-Qing period, and the late-Qing period. The article also demonstrates that, in imperial China, the change of decorative painting style was closely linked to the importance and function of a building.