<p>The steelmaking process in China produces significant quantities of slag, and its chemical composition substantially affects the potential for utilization of the slag. This study has investigated the melting behavior and leaching process of steelmaking slag with different Al₂O₃ contents. The initial melting temperature was observed to increase progressively with increasing Al₂O₃ content. Conversely, the effect of Al₂O₃ on the complete melting temperature exhibited a complex trend: it first decreased and then increased, reaching a minimum at 6.39% Al₂O₃. Al₂O₃ significantly affected the phase composition of the steelmaking slag. At lower Al₂O₃ contents, phosphorus predominantly existed in discrete calcium silicophosphate phases. In contrast, higher Al₂O₃ contents resulted in phosphorus distribution within multi-component solid solutions. The phosphorus leaching rate initially increased and then decreased as the Al₂O₃ content increased. The highest leaching rate occurred at an Al₂O₃ content of 6.39%, primarily attributed to the increased content of Ca₅P₂SiO₁₂. These findings provide valuable insights into the correlation between the slag composition and leaching process of phosphorus, offering a theoretical foundation for enhancing the utilization efficiency of steelmaking slag.</p>