Abstract: The research of consistency degree of fuzzy rules takes an important role in the study of rule base．When determining whether a group of fuzzy rules should enter the rule base,we need to know the consistency degree between the new group and the rules in the rule base．This paper defined the consistency degree of two fuzzy rule groups with the aid of fuzzy relation theory and closeness．Experiments show this definition can include compatible rules and exclude the the rules in contradiction,and this is crucial in the process of building a rule base.

Key words: Consistency degree,Fuzzy relation function,Fuzzy rule group,Rule base