Water injection development is one of the commonly used methods to improve oil and gas recovery in oil fields，but the scaling of injected water will cause blockage of the injected water pipeline and increase the number of pump washing operations， especially in high-temperature，ultra-low permeability reservoirs. The scaling problem will make the formation porosity decrease and the injection pressure increase. In order to solve this problem，the injection water samples and reservoir core of the oil field were taken as the research objects，the scale crystals growth rule of injected water samples was analyzed using particle size analysis，scanning electron microscopy and X-ray diffraction. Combined with the analysis of the core pore structure and mineral composition of the main oil layer，the methods of descaling and anti-scaling was explored. The results showed that the injected water existed in a serious scaling tendency，and the type of scaling was mainly carbonate scale. After the softener was added，the scale crystal grew rapidly in a short time，and the D₁₀ of the scale crystal reached 8—10 μm within 1 h. According to the reservoir characteristics of the target block，a 0.45 μm filter membrane was preferred，and in order to prevent residual ions and scale with smaller particle size from entering the reservoir，a high-temperature anti-scale inhibitors，mainly composed of poly（maleic anhydride），was further preferred，and a combined“softening-filtration-scale inhibition”treatment method was determined to achieve complete prevention of scale formation in injected water.