Abstract: Steel slag droplets will experience a complex process of cooling and solidification after they are granulated by gas quenching.Numerical simulation for cooling dynamics of slag droplets is carried out by Fluent software.The simulation result is compared with that obtained from numerical calculation.It is suggested that the slag droplet undergoes three cooling phases including liquid cooling,release of latent heat and solid cooling.Without considering subcooling degree during solidification of the slag droplet,the consuming time during liquid cooling phase is short through Fluent simulation,while those during release of latent heat and solid cooling phase are long.The shell formation process can be simulated through Fluent software,while the consuming time during liquid cooling,release of latent heat and solid cooling phase can be calculated by numerical calculation.In summary,the total consuming time for cooling from 1 723 K to 1 073 K can be predetermined accurately by both Fluent numerical simulation and numerical calculation,which lay a theoretical foundation for gas quenching process of molten steel slag.