<p>Wettability plays an important role in multiphase flow within oil reservoirs. In many cases, reservoir rocks exhibit distinctly mixed wettability. It is urgent to investigate the water displacement phenomena in mixed-wet porous media. In this work, a method coupled Navier-Stokes and phase-field equations is used to simulate the water flooding process in mixed-wet media. A series of numerical experiments was conducted to investigate the effects of mixed-wet strength and wettability distribution on two-phase distribution, oil recovery, and pressure characteristics. The results indicate that the effect of mixed-wet strength on oil-water distribution becomes more significant when the diameters of water-wet particles are larger. In general, the ultimate oil recovery and the capacity of mixed wettability to enhance oil recovery are higher in mixed-wet media that have larger water-wet particles, compared to those with smaller water-wet particles. The results for the total pressure drop show that a higher driving force is required in mixed-wet media containing smaller water-wet particles. When comparing macroscopic and interfacial capillary pressure, the values are consistently higher in uniformly oil-wet media than in mixed-wet media. By analyzing the microscopic pressure, the microscopic mechanism by which mixed wettability improves oil recovery is revealed: It reduces flow resistance caused by capillary forces or viscous effects. This work provides a preliminary understanding of the impact of mixed-wet strength on oil-water flow, establishing a foundation for further advancements in micro-seepage theory in mixed-wet systems.</p>