Abstract: The confidential theory describes a new approach to inheritance reasoning in nonmonotonic semantic network allowing for multiple inheritance with exceptions. The approach leads to an analysis of defeasible inheritance that is well-defined and intuitively attractive. It yields unambiguous results applied to any acyclic semantic network.Etherington's default logic of inheritance is discussed. It provides a new confidential default logic of inheritance,describes properties of confidential default logic which has unique extension. The process of strutting unique extension is recurrence. The extension of confidential theory can compute quickly. These fast inference algorithms are applicable to expert system.