In his special speech of “The Opening-up of Extenics to Mathematical Basic and Logic”, Prof. Hu Bao-qing of Wuhan University pointed out that extension set breaks through the forbidden zone of concept on set and makes set have a kind of innovative and abnormal characteristics. Extension set is a kind of quantitative tool which could express the process of a matter’s changing from one state or “status” to its opposite. And it also can express the changeable characteristic of things.