Water drive curve and decline curve method for reserves estimation have the problems of time-lagging and hard to reflect the additional reserves increased by adjustment well. By analyzing oil well performance index and applying reservoir engineering and statistics method, it can be found either from theory or field test that the initial rate and decline rate are two main influencing factors for oil well EUR, and the controlling factor for decline rate are reservoir type, single well controlled reserves, initial water content, liquid production and its fluctuation with watercut level. we have correlated decline rate with its’controlling factor and established 19 calculating models for single well EUR which cover reservoir types as water drive, heavy oil, high and low permeability and different well types including straight and horizontal well. An example shows that, using these forecasting models can predict the EUR of new wells promptly and simply with dynamic data such as initial rate.