The leaching behaviors of heavy metals in electric furnace refining slag were studied by total dissolving, short-term and long-term leaching experiments, and the leaching mechanism was analyzed by SEM and XRD. The results show that in the slag, the concentration of Ba from short-term leaching is higher than the discharge standard of wastewater containing heavy metal, and the concentrations of Ni from short-term leaching and V from long-term leaching are higher than the hygiene standard of domestic and drinking water. Leaching of heavy metals is mainly due to the structural damage of Ca2SiO4×H2O (C-S-H) in the slag.