Abstract: Injection wells are corroded severely in Shengli oilfield, combined with injected water quality, the reasons of corrosion are following, high concentration of Cl^-, HCO₃^- and sulfide, and severe bacteria growth. Besides, corrosion factors continuously diverse with the increase of well temperature. High mineral salt concentration and free CO₂ are the major reasons in Dongxin oil field, and growth and reproduce of bacteria is the reason for casing annular corrosion in Xianhe oil field. On the basis of the present situation of injection wells, prevent measures were carried out, consist of using nitrided tubing, selecting corrosion inhibiter and bactericide, and annulus protection technology. Good results were achieved in practice, which have important meaning for extension life injection well.