Yuan-man Wu is an outstanding scholar studying written Chinese characters in Ming Dynasty. ”Liu-shu-zheng-yi” is his most important work on the study of written Chinese characters. The book collects 9353 seal characters. Each regular script is listed behind the corresponding seal character to help recognize seal characters. Significant difference is found between seal characters and regular scripts. This paper aims at study of such difference. The two major reasons to the difference: I. seal characters in ”Liu-shu-zheng-yi” are mainly ancient characters earlier than small seal type characters, which are different from common regular scripts; 2. ”Liu-shu-zheng-yi” adopts common regular scripts, which are different from seal characters. Yuan-man Wu wished to recover the original appearance of written characters through the study of seal characters, and allow the public to use these characters through interpretation using common regular scripts. The purpose of his study is certainly worthy of praise.