The content of ferrous ion is exceeded in the sewage pipeline of an offshore oilfield. The sewage turned black, and a large amount of black scale was found in the sewage pipeline. Component analysis experiment results show that the main components of the scale is ferrous sulfide. In order to stabilize the quality of injection water and reduce pipeline scaling, chemical control of iron deposition was conducted. This paper introduces a new evaluation method of ferrous ion stabilizer for production water. And sodium ascorbate is used to reduce the influence of oxygen in the evaluation effect of ferrous ion stabilizer. Several kinds of ferrous ion stabilizer are optimized. Among them, 30 mg/L of TW-5 is effective, and the solution remains clear and transparent when 50 mg/L of TW-5 is added. Field test shows that TW-5 can improve the water injection quality and inhibit the blackening of the water, as well as prevent the precipitation of ferrous sulfide.