Abstract: With wider and deeper application of the ontologies，ontologies tend to grow bigger and bigger.For specific users or agents，they may be interested in some subsets of an ontology.It is unnecessary for them to operator the huge ontology.So，there is high requirement that user can extract sub-ontologies from an ontology base.According to the shortages of previous research，this paper proposes a user sub-ontology extraction and simplification method that can protect hierarchical relationship，output sub-ontologies without any extra user interference，and reduce the workload of users.

Key words: ontology, sub-ontology, ontology extraction

摘要： 随着本体的应用日益广泛和深入，本体的规模也会变得越来越大。特定用户往往只对本体的某个部分子集感兴趣，没有必要操作巨大的本体，因此，从本体库中提取出用户感兴趣的子本体的需求非常迫切。针对已有研究的不足，提出了一种能够保存本体层次关系的用户的子本体提取和简化方法，方法只需要用户给出的兴趣概念集即可自动输出子本体，不需要更多的人工干预，节省了用户工作量。

关键词: 本体, 子本体, 本体提取