Abstract: The ancients attached great importance to the protection of paper documents, and took many measures to enhance its durability, so as to preserve it for a long time. Many of these measures depended on time and crucial moments. This paper discusses the protection tips related to time from the aspects of the selection of raw materials for paper making, the preservation process of paper documents, and the mounting process of paper documents. It summarizes the protection skills related to the crucial moments from impregnation, cooking, sizing, making the syrup and so on, in order to provide reference for today’s protection work of paper documents.