There are methods and applications for assessing the stability of caverns during the construction period. However, little focus is paid to the maintenance for existing caverns. A maintenance method for existing caverns is focused in this paper and proposed. The continuous monitoring data on the deformation and/or the stress situation of the supports and the surrounding rock are utilized to elaborate a numerical model that fits the current mechanical condition of the cavern. Then using the numerical model, the future behavior of the cavern is simulated under the possible risks, involving the deterioration of the surrounding rock and/or PS anchors. The maintenance criteria are established for the future behavior of the existing cavern based on the results with the comparison to the critical state of the material forming the cavern and the surrounding rock. These processes are summarized as the maintenance flow-chart for the existing caverns.