Abstract: The law of water cut and recovery degreein most of the domestic waterfood oilfield conforms to the S?type curve. This paper derives the relationship between the cumulative water preservation rate and the recovery degree of the S?type curve and presents the method for getting parameters to be determined, based on the S?type curve integrated with material balance equation, thus realizing the conversion of recovery vs. water cut into cumulative water preservation rate vs. recovery degree in theory. The study indicates that regarding the waterflood recovery of the relationship between cumulative water preservation rate and recovery degree as a variate, the chart of cumulative water preservation rate vs. recovery degree in varied waterflood recovery of an oilfield can be drew out, by which evaluation of oilfield waterflood efficiency can be more effective, and the waterflood status can be well revealed or understood. Finally, taking Shanshan oilfield and Qiuling oilfield as example, this paper proposes the suggestions for improving the waterflood effects of them