Abstract: The production decline stage is a main stage of oilfield development, and forecasting oilfield development index in this stage is an important task for oilfield management. The main forecast methods include production decline method, forecast model method, water drive curve method and reservoir numerical simulation method, of which the production decline method is the most effective method. The method is independent of reservoir types and drive types, it can be used when an oilfield enters into the production decline stage. Based on the commonly used exponential decline principle, this paper proposed the methods for forecasting production, total cumulative production,total recoverable reserves, remaining recoverable reserves and reserve?production ratio of an oilfield in this decline stage. The case study shows that these methods are practical and effective