To improve the efficiency of iron recovery from steel slag and reduce the wear-and-tear on facili-ties, a new method was proposed by adding a secondary screen sizer to the magnetic separation process according to grain size distribution of magnetic iron (M-Fe) in the slag.The final recy-cling efficiency was evaluated by calculating the percentage of recycled M-Fe to the maximum amount of M-Fe that could be recovered.Three types of slags, namely basic oxygen furnace slag, desul-furization slag, and iron ladle slag, were studied, and the results showed that the optimized re-covery efficiencies were 93.20%, 92.48%, and 85.82% respectively, and the recycling efficien-cies were improved by 9.58%, 7.11%, and 6.24% respectively.Furthermore, the abrasion be-tween the mill equipment and the remaining slags was significantly reduced owing to the efficient recovery of larger M-Fe particles.In addition, the using amount of grinding balls was reduced by 0.46 kg when every 1 t steel slag was processed.