The efficient utilization of the boron-containing iron ore, China's primary source of boron, has strategic significance for the country. An innovative process that allows for the highly efficient extraction of boron and simultaneous enrichment of magnetite at a relatively low soda-ash roasting temperature (1123 K) under a CO-CO2-N2 atmosphere was proposed. The complex microstructure, composed of spinel (MgxFe3-xO4) and magnesiowustite (MgyFe1-yO), formed concurrently with the activation of boron (NaBO2) when roasting in the presence of 20 wt% Na2CO3. The spinel would be further reduced into magnesiowustite, and the magnetism of roasted samples dropped significantly with increasing CO concentration from 5.0 vol% to 7.5 vol% with a constant CO/(CO + CO2) ratio of 10 %. DFT calculation results demonstrated that Mg-doped Fe3O4 (MgxFe3-xO4) enhances the adsorption of CO molecules and intensifies the reduction of Fe3O4.