Microsphere flooding technology has attracted much attention because it effectively blocks high-permeability channels and improves reservoir flow performance. Based on core flooding experiments and rheological experiments， the dispersion， oil displacement performance， long-term stability， and action mechanism of microspheres in sewage at different concentrations and pH values from Shengli Oilfield were systematically analyzed. The results show that as the concentration of sewage from Shengli Oilfield increases from 0 to 50%， the average particle size of the microspheres increases from 1.2 μm to 2.0 μm， indicating a significant deterioration in dispersion. Under different pH conditions， the average particle size of the microspheres is 2.2 μm in the sewage with a pH of 4， while it decreases to 1.3 μm， showing better dispersion in the sewage with a pH of 9. The core flooding experiments indicate that the oil displacement efficiency of the microspheres is the highest， reaching 50.3%， in sewage with high organic content from Shengli Oilfield. The long-term stability of the microspheres is poor in the sewage at a concentration of 30%， with the average particle size increasing to 2.1 μm after 28 days. The rheological experiments show that microsphere suspensions exhibit shear thickening properties， with a shear stress of 9.1 Pa at a shear rate of 1 000 s^-1. The mechanism analysis reveals that the microspheres interact with impurities and suspended particles in the sewage through electrostatic adsorption， physical adsorption， and chemical adsorption，significantly affecting their dispersion and oil displacement effects.