Rock slopes in open-pit coal mines are subjected to the long-term coupled effects of freeze-thaw cycles and cyclic loading-unloading. To further understand the impact of freeze-thaw weathering on sandstone damage from an energy analysis perspective, stepped cyclic loading-unloading tests were conducted on red sandstone specimens subjected to 0, 20, 40, and 60 freeze-thaw cycles. The freeze-thaw damage to the specimens was quantified using the wave velocity reduction rate and the porosity growth rate. The energy density per cycle and acoustic emission energy during the cyclic loading-unloading tests were then calculated and analyzed. The results indicate that: (1) The damage to the red sandstone intensified with increasing freeze-thaw cycles. After 60 cycles, the wave velocity decreased by 50.83% and the porosity increased by 34.75%. (2) The fatigue stress-strain curves of the red sandstone specimens exhibited a "sparse-dense-sparse" trend. The fatigue strength decreased from 80 MPa? for the unfrozen-thawed state to 40 MPa after 60 freeze-thaw cycles. (3) The total energy density and elastic energy density of the red sandstone specimens showed a "step-like" increase with rising cyclic loading-unloading levels. Prior to fatigue failure, the majority of the input energy was converted into elastic energy, while the dissipation energy fluctuated within a relatively small range. (4) The characteristics of the acoustic emission energy time series can effectively characterize the failure process of red sandstone under the coupled action of freeze-thaw cycles and cyclic loading-unloading. The overall level of acoustic emission energy increased sharply before the instability and failure of the red sandstone occurred. (5) Pre-existing damage induced by freeze-thaw cycles exacerbated microcrack propagation in the red sandstone specimens during the initial stages of cyclic loading-unloading, making damage accumulation more prone to occur. These findings provide a theoretical foundation for assessing and preventing the long-term stability of red sandstone slopes in open-pit coal mines located in cold regions.