Abstract: This paper appraises the benefits achieved by implementing measures in old wells since come on stream of Zhongyuan Field, studies the variation laws of marginal benefit of old well measures, that is, with the uprising of the combined water cut, the marginal cost of the measures rises in the form of index. At the stage of mid-low water cut, it rises in a small scope, while entering the high water cut stage, it rises in a more and more large scope. In addition. this paper probes into the optimization of the measure structure.