Shengli Oilfield is an important oil production and supply base in China，and its main oil reservoirs have generally entered the stage of ultra-high watercut and high recovery，making high-temperature and high-salinity reservoirs the replacement development battlefield. However，due to the constraints of high formation temperature，high salinity of formation water，heavy oil， and scattered distribution of remaining oil， traditional chemical flooding technology has insufficient adaptability in high-temperature and high-salinity reservoirs，facing the bottlenecks of improving economic benefits and recovery. In response to this challenge，researchers from Shengli Oilfield，after over 30 years of theoretical innovation and technological breakthroughs，have developed a theoretical system that includes polymer flooding，additive synergy of polymer，and additive synergy of oil displacement agents，and a technical series of polymer flooding，alkali-free binary composite flooding，and heterogeneous composite flooding. These innovations have successfully overcome the challenge of significantly enhancing oil recovery in reservoirs characterized by formation temperatures of 85 °C，formation water salinity of 30 000 mg/L，and subsurface crude oil viscosity of 2 000 mPa·s. As of June 2025，chemical flooding in high-temperature and high-salinity reservoirs of Shengli Oilfield has reached a produced geological reserve of 6.7 × 10⁸ t and a cumulative oil production of 8 235 × 10⁴ t，with a recovery increase of 9.9 percent points，up to 52.7%. Chemical flooding technology for high-temperature and high-salinity reservoirs is a key guarantee for the sustained，stable production and high-quality development of Shengli Oilfield. The practice of Shengli Oilfield has shown that original innovation is the driving force for technological breakthroughs；integrated innovation is an important means of technological upgrading；iterative innovation is the catalyst for sustainable technological development，and technological synergy is the inevitable trend for mature oilfields to significantly improve recovery rates. With the increasingly stringent conditions of high-temperature and high-salinity reservoirs，it is necessary to develop a theory of multi-dimensional synergistic enhanced oil recovery in the future，tackle new technologies for multi-dimensional synergistic enhanced oil recovery，and provide support for the sustained and stable production of chemical flooding in high-temperature and high-salinity reservoirs.