Abstract: Geomechanical model test and numerical simulation play important roles in stability analysis of large underground caverns at great depth and under high in-situ stresses. Large-scale geomechanical model tests were carried out under true three-dimensional stress state. In order to solve the problem in measurement of small displacements in the surrounding rock masses, the digital speckle correlation method was adopted. Color marks were adhered on the model surface of the caverns, and the PhotoInfor software system was employed to calculate and analyze the vertical displacement of the crown and the convergence values of the side walls. Numerical simulation was also conducted using FLAC3D software under the same conditions, and the results of the model test and the numerical approach were compared. The study shows that the research and the application of the displacement measurement methods used in the surrounding rock masses for large-scale model tests on caverns under 3D stress field have achieved satisfactory results.