Abstract: The complex slurry rheology and low flotation efficiency occur due to the reasons that minerals such as apatite and dolomite in the fine phosphate rock are closely embedded, and fine grinding will produce a large number of fine minerals. In this paper, sodium oleate was selected as the collector to investigate the effects of stirring time, sodium oleate concentration and pH on the hydrophobic agglomeration behavior and rheology of microfine grained apatite and dolomite. By measuring the apparent viscosity values of rheological parameters, the interaction between microfine mineral particles was evaluated to further elucidate the degree of particle agglomeration in the flotation pulp. The research results showed that sodium oleate caused hydrophobic agglomeration on the surface of apatite and dolomite particles. Under the conditions of pH=9, mass concentration of sodium oleate of 200 mg/L and stirring time of 30 min, the average particle size (d_mean) of apatite reached 79.48 μm and the d_mean of dolomite reached 16.47 μm. Under the conditions of pH=5, mass concentration of sodium oleate of 200 mg/L and stirring time of 30 min, the d_mean of dolomite reached 59.74 μm and the d_mean of apatite reached 16.71 μm. pH value was the main factor that affects the hydrophobic agglomeration of microfine apatite and dolomite. Microfine apatite could agglomerate well under alkaline conditions, but the agglomerate degree decreased greatly under acidic conditions, while microfine dolomite was just the opposite, which created favorable conditions for the efficient flotation separation of microfine apatite and dolomite. In addition, the degree of particle agglomeration in flotation pulp correlated with the pulp rheology. As the apparent viscosity of the pulp increased, i.e., the interaction force between particles, especially hydrophobic gravitational force, increased, the microfine mineral particles would aggregate due to hydrophobicity. This study is expected to provide an insight for regulating the hydrophobic agglomeration of fine particles to achieve efficient flotation separation, and will hopefully lay the foundation for strengthening the flotation separation of microfine particles of phosphate ore.