Five main parameters which affect oil field NPV are designed by using design of experiment in this paper, and 25 combinations of the parameters are obtained. Reservoir simulation and economic assessment are used to calculate the NPV, and the regression equations for NPV are obtained by using DOE. The average relative error of 1.21% is sup- posed to be accurate. Optimal production rate and well spacing density are obtained by us- ing three-dimensional map of response surface. This method is good at determining the in- teraction between factors.