Abstract: A method of realization of automatic abstracting based on text clustering and natural language understanding is brought forward, aimed at overcoming shortages of some current methods. The method makes use of text clustering and can realize automatic abstracting of multi-documents. The algorithm of twice word segmentation based on the title and first-sentences in paragraphs is brought forward. Its precision and recall is above 95%.For a specific domain on plastics, an automatic abstracting system is implemented. The precision and recall of multi-document's automatic abstracting is above 75%. And experiments do prove that it is feasible to use the method to develop a domain automatic abstracting system, that is valuable for further study in more depth.