Abstract: Evaluation of residual oil potential with residual oil saturation as the only index can only estimate the watered-out degree in a certain area but cannot give out quantita-tive evaluation results.In view of the specific situations of development at ultra-high water-cut stage in waterflooding oilfields,residual oil potential are divided into3types and6subtypes through calculating economic limits of residual reserves and simultaneously evaluating the abundance of oil saturation and residual reserves.Corresponding potential tapping measures are presented in this paper.