Abstract:In decision table, in order to evaluate importance of one condition attribute, the importance of the condition attribute with respect to decision attribute and the importance of the attribute set which is composed of the condition attribute and others attributes must be considered simultaneously. According to the fact that dependency degree of attribute set is more authentic than dependency degree of single attribute, a new importance degree evaluation method on attribute set is proposed based on discernable matrix. The proposed method can quickly get discernable matrix and directly obtain dependency degree of attributes set, so that time complexity of the proposed method is lower. Examples show the proposed method has better effectiveness and lower time complexity.