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.