Monk Budai by Muxi of the Southern Song Dynasty in the collection of Tokyo Art Club is a valuable and rare work, but it has a severely flocculated surface with fractures and mildew spots, as well as partial loss of the picture and detachment of the mount. This article first discusses the criteria for selection of paper used for the restoration of the painting, from the aspects of paper categories and characteristics found in ancient paintings and calligraphy. In our study, we analyzed the physical and chemical characteristics of the original paper of the painting using modern instruments such as a Fourier transform infrared spectrometer, a pH meter and a microscope, and then conducted a comparison and analysis of five types of repair paper—Xuan paper made in three different times, hemp paper and modern mulberry paper—according to their fiber composition and their physical and chemical properties. We found that the modern mulberry paper matched the original work of Monk Budai best, so modern mulberry paper was chosen for the restoration of the original work. The preparation of the repair paper and the restoration of the work provide a scientific basis and reference for subsequent conservation and restoration.