Abstract: Molybdenum flotation pulps containing a large amount of Ca²⁺, which may precipitate on the surface of Molybdenum with such as \mathrmSO_4^2- , \mathrmMoO_4^2- , \mathrmCO_3^2- , OH⁻, etc., thereby inhibiting the flotation of Molybdenum to varying degrees. The results of solution chemistry calculations indicated that the occurrence points of CaSO₄/CaMoO₄/CaCO₃/Ca(OH)₂/in the slurry were pH=1.8/3.8/6.6/13.6, and there were varying degrees of mutual transformation behaviors. The single mineral flotation test results showed that CaSO₄ and CaMoO₄ had a relatively small inhibitory effect on the flotation of Molybdenum, while CaCO₃ and Ca(OH)₂ had a greater inhibitory effect, with CaMoO₄ having the smallest impact and Ca(OH)₂ having the most adverse effect. The contact angle test results showed that the contact angles on the edges of Molybdenum in deionized water/CaMoO₄ solution/CaSO₄ solution/CaCO₃ solution/Ca(OH)₂ solution were 89.25°/80.44°/73.31°/62.56°/53.13°, which was consistent with the influence of different calcium ion precipitation on the flotation efficiency of Molybdenum. The SEM−EDS results showed that only minimal amount of CaMoO₄ and a small amount of CaSO₄ adsorbed on the edges of Molybdenum, but a large amount of CaCO₃ was adsorbed on the faces and edges of Molybdenum. This indicated that the difference in adsorption behavior of different calcium ion precipitates on the surface of Molybdenum might be the reason for the different flotation effects of Molybdenum. Therefore, regulating the type of calcium ion precipitate in the flotation slurry of Molybdenum is beneficial for improving the molybdenum selection effect.