Iron-rich phases mainly existing in the form of acicular-like in coarse Al?Si alloy has detrimental effects on the mechanical property of the alloy, which is urgently needed to be solved before used as materials for producing casting Al?Si alloys. Based on the traditional metal impurity removal theory, iron-rich phases in the coarse Al?Si alloy (Fe content 5wt%) can be removed by adding manganese during the electromagnetic directional solidification process, which mainly improves the structure and shape of iron-rich phases and reduces iron content to decrease the harmful influence of iron-rich phases on mechanical properties of Al?Si alloy. The effects of Mn addition on the removal rate of iron-rich phases from Al?Si alloy, influence of Mn on the improvement of morphology of iron-rich phases, and the separation mechanism were studied. The results showed that with the moderate increase of manganese addition, iron-rich phases in Al?Si alloy combined with Mn to form some complex intermetallic compounds with larger shape factors, decreasing the migrating resistance of iron-rich phases when conducting the electromagnetic directional solidification. The migrating velocity of iron-rich phases could be improved as the majority of iron-rich phases in the Al?Si alloy got regularized in shape and structure, therefore the separation efficiency of iron-rich phases was enhanced as well. Eventually, iron-rich phases could be enriched at the bottom of the alloy by the electromagnetic force as a result of larger magnetic susceptibility than that of Al melts. This new technology to remove iron-rich phases from coarse Al?Si alloy had the characteristics of high-efficiency, cost saving, environmental-friendly and energy conservation. It could hopefully become the substitute for preparing casting Al?Si alloy after the electro-thermal process, because not only iron-rich phases in Al?Si alloy were removed, but also primary silicon was accumulated at the bottom of the alloy. In other words, impacted by electromagnetic directional solidification and Mn addition, the purified alloy was divided into two parts: the upper Al?Si alloy with low iron and silicon contents, and the bottom impurity accumulating parts of Si and Fe. The residual iron content in Al?Si alloy was reduced to 0.39wt%, with the iron removal efficiency reaching 90%.