Abstract: Chang 9 reservoir in Honghe oilfield is a typical low porosity and ultra-low permeability reservoir with poor physical properties and low percolation capacity of formation fluid. In the process of water injection development, the oil pressure difference of injection water drive is high, some water injection well groups show that the corresponding oil wells do not increase oil, and the effect of water injection development is poor. The analysis shows that by reducing the oil-water interface tension and reducing the oil saturation of the reservoir, the displacement pressure difference can be effectively reduced. According to the laboratory test evaluation, the developed microemulsion pressure reducing and augmented injection system can reduce the water drive pressure of reservoir core by 28% ～ 70%, achieve the purpose of improving the oil displacement effect, and has a good prospect of application.