Abstract: A large number of electronic documents will be produced in daily working year after year. In accordance with the confidentiality regulations, all the documents should be marked with the corresponding security classification on the first page. The normal practice is to manually insert a text box on the first page of the electronic document and input a formatted security classification. In order to reduce the repetitive operation, the document security classification marking software is designed based on VBA, and the program entry is integrated into the right mouse button menu bar. The security classification of the selected documents can be automatically marked without opening it. The result shows that each electronic document takes about 20 s to mark security classification with the same type, size, location. The working efficiency is greatly improved, and it has certain application and popularization value.