Ancient rare books are the documents for which there exists maximal contradiction between their usage and preservation while the best way is to digitize them.The fulltext data entering should keep the original appearance of the rare books.The Chinese Ancient Rare Books Image Retrieval System produced by the Shanghai Library can transfer the fulltext data into CD ROMs as images and the functions of the indexing,searching and browsing as well ,which serves as a good attempt to digitize the ancient rare books.