Abstract: This paper discusses the necessity to process the character out the set from the angle of the research and prac- tice of digitization of ancient books. The method of processing the character out the set and their features are introduced, including replacement method, the description method and the creating character method. Taking the project of the electronic version of Si Ku Quart Shu and digital local records as examples, this paper puts forward processing programs of character out the set and its evaluation methods.

Key words: character out the set; digitization of ancient books; character set