In fact, citations are not duplicate checking, but for citations, duplicate checking software has strict writing format requirements. If the format is correct, it will not be recorded in duplicate checking, while if the format is wrong, it will probably be copied as the text of the paper. The main content of duplicate checking in extended information knowledge network is the abstract and text of the paper, including the quotation. It is not easy for different schools, periodicals and magazines to check the duplicate, but the duplicate checking system will not check the picture information and other contents in the paper because there is no way to compare them.