Abstract: The excavation and unloading of underground rock engineering will strongly disturb to the original in-situ stress, which may cause instability, rock burst, and other disasters. In this paper, the conventional triaxial and loaded and unloaded triaxial comparison tests were carried out on red sandstone to obtain the mechanical properties, failure characteristics, and energy evolution laws of sandstone under different unloading points. The results show that the peak strength and elastic modulus of unloaded rock samples are smaller than those of conventional rock samples, indicating that unloading confining pressure will affect the mechanical properties of sandstone. The failure mode of the unloaded rock sample is more complex than that of the conventional rock sample, and it also shows more obvious characteristics of expansion deformation due to the unloading of confining pressure. The total strain energy, elastic energy and dissipated energy at the characteristic stress point are all met: no unloading >85% unloading >75% unloading >65% unloading, indicating that the higher the axial stress is, the more elastic energy will be released when the rock breaks, which is proved by the destructive effects of local high-stress rockburst disasters in practical engineering. The inhibiting effect of confining pressure can increase the storage of elastic energy and reduce the release and dissipation of energy. Internal cracks and crack propagation are important reasons for the rapid accumulation of damage variables and the rapid release of energy.