The problem of high pressure underinjection in ultra-low permeability reservoirs is prominent, and the validity period of conventional acidizing injection is gradually shortened. Small pore throat and complex structure are the root causes of high starting pressure and high seepage resistance. How to keep pore throat unblocked and eliminate blockage is the key to improve seepage capacity. Molecular film drag-reducing injection enhancers, as a new injection enhancer, have been widely used in eastern oil fields in China. The surface/interfacial tension, wettability, swelling resistance, temperature and salt resistance and adsorption strength of molecular film were evaluated by water ion analysis, compatibility evaluation, scaling experiment and trend prediction in Changqing Oilfielaboratory. The molecular film drag-reducing and injection-increasing dosage forms suitable for ultra-low permeability reservoirs in Changqing Oilfield were selected, and the construction technology was optimized. Field application shows that this measure can significantly reduce the injection pressure and increase the injection volume, thus achieving the effect of increasing oil.