The invention discloses a kind of auto question-answering system, which includes interface unit, illation unit, language knowledge base, illation knowledge base, normalization table of keyword, and normalization unit, the illation unit inquires said illation knowledge base according to sequence of normalization to find the answer corresponding with the question with same sequence of keyword, and the answer is as the system response to be output by said interface unit. The invention also discloses a kind of auto question-answering method, which can be used in the system with language knowledge base, illation knowledge base, normalization table of keyword, and it can divide the input question; and the normalization is done for the sequence of keyword; and the normalized keyword can find the setting question with same keyword; and it can search the answer according to the question; and said answer is output as system response. Thee invention can reduce the working capacity for building illation knowledge base by the normalization of synonymous keywords.