The Hall of Mental Cultivation (Yang Xin Dian) is located on West Road, inner court. Yan Xi Tang is on the west side of back palace of Yang Xin Dian. This article is part of the project—“Studies on the paper based artwork in the Yang Xin Dian”—which is a sub-project of the research for the protection of artwork in the Forbidden City. Investigation of the type and distribution of Biaohu paper has been done. Combined with the documentary records, the cross-section of the multilayers, the paper fibers and pigments were analyzed. The investigation and study of the Biaohu paper in Yan Xi Tang, provides a scientific basis for the restoration work.