Abstract: The extension method and principle of trouble diagnosis are expounded. The tool storage of machining center is served as being researching object. The trouble diagnosis problem of tool storage is studied thoroughly based on the method of extension diagnosis. The method of the implication system and the conjugate pair that is used to analyzes troubles of the tool storage. And put forward that the trouble diagnosis method based on the extension method, which not only can well and truly judge the trouble that has happened already, but also can find the hidden trouble by the conjugate analysis. And reduce the losing. It is accurately calculated to the degree of the trouble happening by using the dependent function. A new method in which the quality combined with the quantity for the trouble diagnosis is provided. Thereby, the new method made the diagnosis more objectively and completely.

Key words: Analytic hierarchy process, Extension theory, Tool storage of machining center, Trouble diagnosis