Abstract: The properties of flotation foam within a flotation system play a crucial role in its interaction with mineral particles, directly impacting the efficiency and selectivity of the entire flotation process. Currently, most collectors exhibit favorable foaming properties, and the formation and characteristics of the foam in the collector system significantly affect the regulation of the mineral flotation process. Given the poor selectivity of conventional anionic collectors in magnesite flotation, developing new collectors has become a hot topic in mineral processing research. Investigating the relationship between foam properties and flotation outcomes is significant for optimizing the mineral flotation process and enhancing the utilization rate of mineral resources. Previous research has revealed that potassium cetyl phosphate can selectively adsorb on magnesite surfaces, enabling effective flotation separation of magnesite from calcium-bearing gangue minerals. This suggests significant application prospects for potassium cetyl phosphate as a new anionic collector in froth flotation purification of magnesite ores. However, to our knowledge, the foam properties of this collector have not been extensively studied. This study employs the DFA 100 Dynamic Foam Analyzer to systematically investigate the foam properties of two anionic magnesite collectors. Key performance differences, including foaming characteristics, foam stability, and structural integrity under various pH conditions and different Mg²⁺ concentrations resulting from mineral dissolution, were examined. A comparative analysis relative to the conventional sodium oleate collector systems was also conducted. The results indicate that, under identical mass concentration conditions, the surface tension of the cetyl phosphate ester collector varies more gently. As a novel anionic magnesite collector, CP demonstrates significantly superior foam adaptability under changing pH values and Mg²⁺ concentrations compared to the traditional sodium oleate (NaOl) collector. Specifically, within the studied ranges of pH values and Mg²⁺ concentrations, cetyl phosphate exhibits superior foaming propensity and more pronounced foam stability. Notably, the foam structure generated by cetyl phosphate is more stable, with inhibited foam coalescence observed at elevated pH values. By contrast, the NaOl collector loses its foaming ability in solution environments with pH values below 8.0 and Mg²⁺ concentrations exceeding 20 mg·L⁻¹. Single-mineral flotation tests further confirm the consistency between the flotation rate of magnesite and the impact of the solution environment on the foam properties of both collectors. Under conditions where the pH is below 6.0 or the Mg²⁺ concentration exceeds 30 mg·L⁻¹, traditional collector NaOl struggles to capture mineral particles during magnesite flotation. By contrast, the flotation rate of magnesite with the cetyl phosphate collector remains above 60%. The experiments also revealed that the microstructure of foam generated by the cetyl phosphate collector has a more uniform size distribution and a more compact foam layer structure. These characteristics are crucial for improving the collection efficiency of mineral particles and enhancing the selectivity of the flotation process. This study provides a solid theoretical foundation for the application of phosphate ester collectors in magnesite flotation through an in-depth analysis of foam microstructure and a comprehensive comparative assessment of foam properties between phosphate ester and oleate collectors under varying solution conditions. Furthermore, this study offers valuable practical insights for efficient collector selection and flotation process optimization in industrial applications. These insights contribute to advancing magnesite flotation upgrading technology and processes. The results presented in this paper also serve as an important reference for optimizing the theory and practice of calcium and magnesium salt minerals. This is significant for the development of flotation technology.