The invention provides a production process for preparing a high-iron-grade product and calcium magnesium acetate from an RO-phase-containing material. The RO-phase-containing material is added into an acetic acid solution; stirring reaction is performed, so that non-FeO ingredients in the RO phase and hydrated active minerals in the steel slag are sufficiently dissolved; still standing is performed so that the non-dissolved residue is sufficiently settled, and the solution layers; supernate is extracted to obtain the calcium magnesium acetate solution containing acetic acid; settled materialsare subjected to extraction filtering and dewatering to obtain the high-iron-grade material which can be used as iron making concrete powder making or heavy medium powder for coal dressing; the calcium magnesium acetate solution containing acetic acid is heated to 1 to 50 DEG C to obtain the calcium magnesium acetate powder dried by distillation; the calcium magnesium acetate powder can be used as a desulphurization and denitrogenation agent for fire coal or environment-friendly snow-melting agent. The selective dissolution effect of the acetic acid solution on the RO phase ingredient is used; the MgO, CaO and MnO ingredients in the RO-phase-containing material are dissolved out; the high-grade iron concretes are obtained; a new technology is provided for the steel slag resource utilization; the operation of the technical process is easy; waste gas, waste water and industrial slag cannot be generated; the operation cost is low.