Abstract: Knowledge reduction is considered as one of the most important aspects in rough set theory.At present，there are many algorithms about knowledge reduction，but the majority of these ways focus on the consistent decision system.For most of the decision systems are not consistent in applications，it is meaningful to approach ways for achieving knowledge reduction in inconsistent decision systems.Against the “distinguishable relation” and “distinguishable set” concepts，the “reduction based on decisive including degrees” and “reduction based on maximum decisive including degrees” concepts are given in this paper.The relationship between these reduction terms is examined.Per discussing on that，the result，“reduction based on decisive including degrees” is stronger than “reduction based on maximum decisive including degrees”，is easy to conclude.In this paper，new concepts and ways are introduced to figure out knowledge reduction in inconsistent decision systems.Also，all of them can apply to consistent decision systems.

摘要： 知识约简是粗糙集理论中的一个重要内容，目前大多数研究都集中在协调的决策信息系统上。但现实中存在大量的不协调决策信息系统，针对该类系统的约简研究，将更具有实践意义。定义了决策包含度约简和最大决策包含度约简的概念，讨论了决策包含度约简和最大决策包含度约简的关系，即最大决策包含度约简弱于决策包含度约简，为解决不协调决策信息系统的知识约简问题提供了新方法。