Abstract: The concepts of positive association rule and negative association rule are redefined，and the interest degree of the rules is brought out.Therefore，the evaluation standard of the positive and the negative association rules is conformed.On the basis of the above，the inconsistency of association rule set is solved tentatively by logical method and its expressive power is increased further.As a result，the author optimizes the original association rule set.

Key words: data mining, association rule, evaluation