With the continuous utilization of magnesite resources, the high quality magnesite resources are depleting, and the high-efficient development of low quality magnesite ore has caused extensive interests of researchers. The main gangues in magnesite ore are quartz and dolomite. Recently, successful desilicication for magnesite ore has been carried out. However, it is still a big problem for the effective removal of dolomite from magnesite. Thus, in order to make the removal of dolomite during desiliciation process clear, the effect of such metal ions as Ca²⁺, Mg²⁺ and Fe³⁺ on flotation of magnisite and dolomite was investigated. Flotation results for single minerals indicated that flotation recovery for dolomite could be as high as 78.33% when dodecylamine concentration was 200 g/t at a slury pH of 8.5. Nevertheless, the flotation recovery was only 24.68% for magnesite. The addition of Ca²⁺ and Mg²⁺ was not useful for the flotation of magnesite and dolomite was drepressed. However, the addition of Fe³⁺ could active the magnesite and dolomite flotation. When the concentration of Fe³⁺ was less than 200 g/t, the flotation of dolomite was activated significantly, while the flotation recovery of magnisite was kept steadily. When the concentration of Fe³⁺ was 60 g/t, optimized separation results for magnesite/dolomite mixture could be obtained with 38.83% MgO grade and 58.13% magnesite recovery in concentrate. Compared with no addition of Fe³⁺, more than 13% magnesite recovery in concentrate was increased obviously when MgO grade in concentrate was kept steadily.