Abstract: Extension detecting is a new detecting method that is based on the extension analysis method of extenics.Many detecting problems that can not be solved with the traditional detecting method can be detected in the way of detecting the detectable matter-element rather than the undetectable matter-element based on the extension transformation method.Related matter-element is a bridge to connect the undetectable matter-element and the detectable one.The method of finding related matter-element and its application in the extension detecting are presented in the paer.

Key words: extension detecting； matter-element； related matter-element； association rules；