Abstract: In recent years, Chang-6 ultra-low permeability reservoir of Honghe Oilfield has reduced production decline by means of water injection, but there are also problems of high water injection pressure, insufficient injection and even water injection failure, the formation energy can not be replenished effectively. The analysis showed that the main causes for insufficient injection in Chang-6 ultra-low permeability reservoir were poor reservoir properties, low permeability and small pore throat radius; the secondary causes were not compatible with injected water and formation water as well as scale formation. Additionally, clay swelling and migration in the water injection process could also reduce the reservoir permeability. In order to solve the insufficient injection problem in the reservoir, the polybasic recombination acid technology has been introduced. Laboratory test results showed that the polybasic recombination acid was highly compatible with injected water and formation water, and it could provide low corrosion rate and clay swelling rate, and keep slow rate of core dissolution. According to field applications in eight wells, the polybasic recombination acid technology can eliminate pollution near water injection well, restore and improve formation permeability to achieve decompression and augmented injection.