<p>The continuous enrichment of phosphorus in the double slag steelmaking process affects the structure and properties of steelmaking slag. In this study, the effect of P₂O₅ on the structure and transport property of CaO-SiO₂-P₂O₅-FeO melts was investigated by molecular dynamics calculation. The results indicate that, with the increase of P₂O₅ content, the Ca-O bond length increased and the Fe-O bond length decreased, the Si-O and P-O bond lengths fluctuated around 1.61&#xa0;Å and 1.54&#xa0;Å, respectively, and the [SiO4]^4- and [PO4]^3- tetrahedral structures exhibited stability. The proportions of FO and BO decreased from 25.10% and 23.10% to 13.70% and 19.60%, respectively, while the proportion of non-bridging oxygen increased from 51.90% to 66.70%, and the aggregation degree of the system showed a decrease tendency. As the P₂O₅ content increased, the self-diffusion coefficient of Fe²⁺ ions increased significantly from 7 × 10⁻⁶ Ų/ps to 1.42 × 10⁻⁴ Ų/ps, P⁵⁺, O²⁻, and Ca²⁺ ions also showed an increasing trend, whereas Si⁴⁺ showed no significant change. Concurrently, the structural aggregation of the system decreased.</p>