Abstract: The influential factors on reservoir production capacity can be divided into artificial factors and reservoir factors. The reservoir production capacity depends mainly on reservoir itself on condition that the: artificial factors are basically the same. Beginning with the Darcy's two -dimensional production equation, a theoretical equation of reservoir production capacity is derived and the multivariate function between reservoir production capacity and reservoir effective porosity, permeability and resistivity is established through tile use of the functional relation between relative permeability and water saturation. On base of the above studies, a reservoir production capacity predicting system is established with grey association analytical method. This method not only can comprehensively and quantitatively evaluate the categorization of reservoir production capacity but also can give out the reliability of evaluation results through relation degree. Its effectiveness has been verified by the predicted production capacity of the Keshang Formation in the District 8, Kelamayi oilfiled.