<p>High ground temperature and unloading disturbance have emerged as critical factors impacting the property of cemented gauge-fly ash backfill (CGFB). The characteristics of energy and damage in CGFB were analyzed under conditions of high ground temperature and unloading by conducting triaxial unloading tests with different initial confining pressures on CGFB that had been cured at various temperatures. Based on dissipative energy, triaxial unloading confining pressure damage constitutive model of CGFB was constructed. It has been demonstrated that the ratio of elastic strain energy in CGFB decreases and the ratio of dissipated energy increases at the end of unloading increases under higher curing temperature. The change in the elastic energy consumption ratio curve of CGFB, which shifts from a gradual increase to a swift rise at a certain “inflection point”, can be utilized as a criterion for evaluating the failure of the unloading strength of CGFB. The triaxial unloading damage constitutive model for CGFB divides the damage progression into three distinct phases: initial damage stage, accelerated damage development stage, and rapid damage growth stage. The research findings offer a theoretical foundation for evaluating the extent of damage to CGFB caused by the combined influences of elevated ground temperature and unloading.</p>