Along with the oilfield entering into extra high water cut stage，the fracturing objects of water driving oil wells are becoming poor，and also the selection of fracturing wells and layers is more and more difficult. Based on reservoir engineering and real oilfield situation，we selected and analyzed the main influencing factors of fracturing effects by using multiple correlation and grey association methods, including effective thickness of the fracturing layers，permeability of the fracturing layers，ratio of formation coefficient of the fracturing layers to formation coefficient of the whole well，water cut of the whole oil well before fracturing， fluid quantity per day of the whole oil well before fracturing and pressure difference before fracturing. We used the group method of data handling （GMDH）to establish the regression model between the fracturing oil production enhancement and the main influencing factors, used the input-output principle of economics to establish the economic limit model of fracturing oil production enhancement，and defined that whether the fracturing oil production enhancement is economic or not is related to fracturing inputs and corresponding change of cost.