Prefaces and Postscripts of Paintings and Calligraphies and Coral Net were compiled successively in Jiaxing County, Zhejing Province during the reign of Emperor Chongzhen in the Ming Dynasty. These two books are both catalogs of paintings and calligraphies in the style of collecting prefaces and postscripts. Coral Net and its compiler WANG Luo-yu are more famous, which are frequently quoted by appreciators of paintings and calligraphies in past dynasties. By comparing these two books, however, one can find that many prefaces and postscripts are respectively recorded in them. Coral Net copies a lot of sentences and ideas from Prefaces and Postscripts. Technical methods such as changing word order and revising relative signature in order to conceal the fact of plagiarism. The limited spread of Prefaces and Postscripts leaves space for Coral Net to plagiarize. WANG Luo-yu’s advantages in his family reputation, his wide circle of acquaintances and his influence result in a higher position of his book in later generations. The fate of YU Feng-qing, as well as his lower status, his difficult situation in life and work, was common among public cataloguers of paintings and calligraphies. This also reflects the big problem of seeking academic sincerity.