Abstract: Based on the corrosion investigation in reinjection pipelines from 7 sewage plants in Shengli Oilfield, the paper adopts grey correlation method to analyze correlative degree of all the factors affecting on sewage corrosivity, and then obtains a correlative degree sequence. It shows that main effective factors on sewage corrosivity in reinjection pipelines of sewage plants in Shengli Oilfield are total salinity, SRB and dissolved oxygen contents. A grey dynamic model reflecting the change of corrosion rate with time is developed by GM(1.1) system mode and it is used to predict corrosion rates. Prediction results have good agreement with measurement data.