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The removal mechanism of Ca2+ and Mg2+ ions affecting apatite ore flotation index by synergistic action of three pH regulators (Na2CO3, NaOH, and NaHCO3) was investigated. A moderate amount of Ca2+ and Mg2+ in the slurry is favorable to improving the flotability of apatite minerals, but an excessive amount of Ca2+ and Mg2+ not only increases collector consumption in apatite flotation but also negatively affects the concentrate grade and recovery by forming a hydrophilic film on the surface of the mineral. The optimum addition condition of pH regulators was determined by considering the anion concentration distribution of industrial water. In the presence of CO32-, HCO3- and OH- simultaneously in the slurry, Ca2+ and Mg2+ are more effectively removed due to the simultaneous formation of carbonate, bicarbonate and hydroxide by the synergism of the anions to provide more positive conditions for apatite flotation compared to the addition of individual regulators separately. The proper concentration ratio of CO32-, HCO3- and OH- was 2:1:1 and Ca2+ and Mg2+ were removed 93.8% and 87.2%, respectively.