The high-temperature roasting of red mud can realize the form transformation of iron, aluminum and silicon, making it easy to separate and recover. However, there are few reports about the difference and mechanism of sodium reduction roasting reaction of high iron and low silicon red mud. The effects of reduction temperature, Na2CO3 addition and reduction time on the phase transformation and microstructure of high iron and low silicon red mud were investigated by X-ray diffraction analysis, and the difference of iron magnetic separation after reduction reaction was also analyzed. The results show that sodium combines with aluminum and silicon elements to form sodium aluminosilicate during reduction roasting, which effectively destroys the compact structure of Fe and Al elements. Hematite and goethite are converted into magnetite and wustite mostly, which promotes the reduction of iron oxides. The low melting point sodium-containing solid solution reduces the migration resistance and accelerates the growth of metal iron grains. Based on the disintegration of the Fe-Al structure and the formation of coarse-grained metal iron, the roasted product is subjected to grinding-magnetic separation, and iron recovery indicator with the TFe content 90.41% and Fe recovery rate 93.08% is obtained.