A mathematical model of the metal droplet settlement process of smelting slag was established. The effect of interfacial tension between the metal and slag phases on the droplet settlement velocity and drag force under different viscosity models was studied. The results showed that the Laminar and RNG k-ε turbulence models accurately predict the final settlement velocity of smaller diameter droplets. The interfacial tension affects the settlement velocity of the droplet, and the effect gradually increases as the droplet size is increased. The “RNG + CSS” model accurately describes the droplet settlement process and the change in the droplet settlement velocity. The drag force coefficient formula under coupling interfacial tension was derived with the established mathematical model and experimental data. This model reveals the mechanism of the settlement process of metal droplets in smelting slag and provides theoretical guidance for reducing the content of valuable metals in slag in actual production.