Abstract: Based on DST testing data for 12 wells in A-Nan oil field, fuzzy design method is used to study relationships between effective permeability and electric logging permeability, formation pressure coefficient, electric logging porosity, water-cut, overburden pressure and minimum main horizontal stress. The factors considered in this paper are more completely and a gray correlation method is introduced ingeniously to determine weight. It overcomes the shortcomings to determine weight in previous method and makes it more quantitatively. It is proved that the effective permeability achieved by this method keeps coincidence with the value derived from the method of reservoir numerical simulation matching.