Abstract: In order to explore the environmental risk of waste acid gypsum sludge produced by the thermal copper refining process, the long-term stability and heavy metal release characteristics of waste acid gypsum sludge were investigated using the methods of simulated stockpiling, static erosion, and semi-dynamic erosion. The findings indicate that the waste acid gypsum sludge has a leaching concentration of As and Cd that is higher than the standard (1488.66 and 22.98 mg/L, respectively), with As reaching an acid-extractable state of 87.55% and Cd effective state exceeding 90%, which poses a serious environmental risk. The results of the simulated stockpiling demonstrate that shower loss and dust should be prevented because waste acid gypsum sludge poses a serious ecological risk level. As and Cd adhered to the surface of waste acid gypsum sludge are leached out in significant amounts by chemical reaction and diffusion during static and semi-dynamic erosion, resulting in concentrations that are all quite high. Among them, the leaching concentration of each element in the landfill simulation environment is significantly larger than that in other simulation environments, which requires special attention.