Abstract: The deformation and failure of rock are closely relative to energy change. Experiments are carried out to investigate marble samples under triaxial compression by means of the servo-controlled testing machine. Based on the experimental results, the energy numerical variable is calculated and interpreted, and the internal relations among energy numerical variable, confining pressure, stress and strain are studied and compared. The results show that the failure strain energy of marble samples increases to a considerable extent as the confining pressure increases. The energy change has a positive linear relation with the stress and strain respectively of marble samples under vested confining pressure. With the increase of the confining pressure, the slope of energy change-deviatoric stress curve reduces, and the slope of energy change-strain curve accelerates. In the triaxial compression process, the amount of energy change at the elastic deformation stage takes a small proportion of the total energy change. Most of the energy dissipates at the yield deformation stage. At the same time, the amount of energy change at the yield deformation stage takes a greater proportion in the total energy change as the confining pressure increases.