Abstract: For fuzzy knowledge and its variety of negative relations，Pan points out that the negation in fuzzy knowledge should be composed of three distinct classes：contradictory negation，opposite negation and medium negation，and proposes the Fuzzy Sets with Contradictory negation，Opposite negation and Medium negation denoted as FScom.Based on which，the set fundament of fuzzy knowledge and its different kinds of negations is further investigated and one kind of improved fuzzy set with three kinds of negations denoted by IFScom is proposed，meanwhile its characteristic，operation and related properties are also investigated.The given demonstration shows that it is valid to defferentiate，represent and infer about the various negations of fuzzy knowledge with the improved fuzzy set IFScom.

Key words: fuzzy knowledge, negations, fuzzy set, medium logic

摘要： 对于模糊知识及其否定关系，潘指出应该明确地分为矛盾否定关系、对立否定关系和中介否定关系，并建立了一种具有矛盾否定、对立否定和中介否定的新模糊集FScom。在此基础上，对模糊知识及其各种否定的集合基础进一步研究，提出了一种改进的具有三种否定的模糊集IFScom，并讨论了它的特征、运算及相关性质。应用实例表明改进的模糊集IFScom在模糊知识的“否定”的区分、表示以及推理上是有效性的。

关键词: 模糊知识, 否定, 模糊集, 中介逻辑