In the novel process, iron oxide red wastewater was pumped into the neutralization aeration tank, reacted with 30 wt.% industrial caustic soda added through a pipeline mixer. pH was adjusted in the tank and most of Fe2þ changed to Fe(OH)2 and Fe(OH)3, then change to a-FeOOH or g-FeOOH by abundant aeration, which also played a role of stirring in the reaction.