To study the sulfate resistance of ultra-high performance concrete (UHPC) in saline soil area of western China, four kinds of sulfate solution concentrations (0 %, 5 %, 10 %, 15 %) and 18 drywet cycle tests for 540 days were carried out on UHPC specimens. The effects of sulfate dry-wet cycles on the evolution of UHPC strength and energy were studied, the characteristic stress points during uniaxial compression of UHPC under sulfate dry-wet cycle were determined, based on the evolution law of each energy (total energy U , dissipated energy U d , elastic stress U e ) at the characteristic stress points, the energy storage index was established to measure the damage degree of UHPC. The results show that the energy evolution process and damage mechanism of UHPC samples under sulfate-wet and dry cycle erosion are closely related to macro and micro changes. With the development of sulfate dry-wet cycle, the dissipative energy U d and elastic strain energy U e of UHPC at the characteristic stress points increased first and then decreased. The development trend of elastic strain energy U e and dissipative energy U d is more severe with the increase of sulfate solution concentration. The ratio of elastic strain energy at damage stress to elastic strain energy at peak stress ( U e ib /U i e ) is taken as the energy storage index K ib to measure the damage degree of UHPC, under 10%Na 2 SO 4 erosion, K ib can be increased by 21.41 % at the highest and decreased by 29.67 % at the lowest compared with the initial value. It shows that the damage process of UHPC is difficult and then easy, and this index can accurately reflect the external force required for the damage of UHPC under sulfate dry-wet cyclic erosion, and provide a reference for the safe and stable operation of UHPC in saline soil area.