Low-permeability reservoirs are characterized by poor physical properties and mini pore throat. Due to their low permeability and the Jamin effect, they are often encountering difficulties in water injection. According to Darcy’s law, flow rate is directly proportional to pressure difference and permeability. While fracturing can enhance the reservoir properties near the wellbore, it cannot effectively sweep the area between the injection and production wells. Improving the injection pressure and increasing the displacement pressure difference can increase the liquid volume and production of the corresponding oil well. Therefore, laboratory experiments, theoretical research, and practical applications were carried out practice. Laboratory tests have confirmed that the displacement pressure gradient has an impact on the two-phase flow characteristics of oil and water in low-permeability reservoirs. Enhanced the displacement pressure results in changes to the ends of the oil–water relative permeability curve, a larger co-permeation area, and a reduction in the starting pore throat radius. The reasonable injection pressure should be higher than the reservoir start-up pressure and lower than the fracture pressure and the maximum pressure required by oil recovery engineering. The value can be obtained and calculated based on reservoir characteristic parameters and laboratory experiments. Productive practice has shown that increasing the injection pressure in water injection wells enhances the water absorption profile, improves the producing degree and increases the production of corresponding oil wells within the well group. Under the fracturing pressure, determining the reasonable maximum injection pressure, combined with acidizing, fracturing and other injection methods, can effectively improve the production of corresponding oil wells.