Abstract:For the royal mausoleum, the construction of underground buildings is undoubtedly the most important. This paper takes the most representative yuling underground palace as an example, through the detailed investigation of the installation of "Longmen arch", combined with the royal archives, calculated , and reached an important conclusion that the underground palace arch stones using prefabrication form, not only made a breakthrough in the study of mausoleum buildings, but also filled a big gap in the research of Qing dynasty official masonry.