Diary is a kind of literature type and writing method, which has a long tradition in China. As a kind of micro historical materials, diaries have the ability to reflect the overall history, especially those that have been recorded for a long period of time or have special identities. Their significance is not only in the personal life history, but also has many values and connotations such as political history, economic history, social history, and cultural history. To some extent, diaries can be seen as a microcosm of the times and have the nature of an encyclopedia. It is undoubtedly of great significance to have a glimpse of the times and reveal the social and historical situations in which the characters are exposed. A large number of existing diaries were mainly produced in modern times. The magnificent changes of the Chinese civilization during this period were not only seen in the official history of the emperor, but also expressed in many private documents. Since 2014, Zhang Jian, Xu Yanping, Peng Guozhong and others have successively launched the "Rare Historical Materials Series of Modern China" with diaries as the main content in the form of an annual edition. At present, nine editions have been published and more than 100 kinds of diaries have been sorted out. Recently, another series of "Journal Studies" has been published. Although there are only five kinds of "Journal Studies of Tan Xian's Manuscripts", "Boat of Transition: Studies on Hu Shi's Diary of Studying Abroad", "World Sentiments, Characters and Literature in the Diaries of the Late Qing Dynasty", "Private History Microscopy: Multiple Perspectives of Modern Chinese Writers' Diaries", and "Chang Shu Weng's Diary Studies", they can also be seen as a big step forward from the sorting of modern diaries to the study of modern diaries. Diary, as an important writing method that not only constructs self, but also carries collective memory, has an important value that can not be ignored for understanding the historical changes of China and the "history of mind" of Chinese people. At present and for some time to come, it is extremely important to explore the historical materials and documents of modern diaries, start with the study of the history of daily life, deeply describe the reading history, emotional history, and psychological history of Chinese literati and modern writers, and reflect on the nature of diaries, the academic value and limitations of diary research. The most prominent feature of diary is "diary keeping". Most people often assume that diary is a kind of "private text" in the process of reading diary. However, does diary really belong to a kind of text with strong privacy? This can be checked by observing the generation process of diary text. In Changshu Research on Weng's Diary, through reading Weng Xincun's and Weng Tonghe's diaries, Jia Hongtao found that Weng's father and son were highly consistent in writing order, tone and wording, emotional expression and even location arrangement, except for similar descriptions of common events in their diaries. It is speculated that Weng's father and son lived together in the capital at that time, In the process of recording the diary, it is possible to borrow the diary of the other party or exchange the way of writing the diary. The same research mode also appeared in Tang's research on Hushi's Diary of Studying Abroad. Tang believed that there were two different writing styles, namely "diary" and "notes", in the previous and subsequent periods of Hushi's Diary of Studying Abroad, and they each assumed different stylistic functions. Hu Shi's use of "notes" as a writing diary had a clear desire and appeal for publication, which was different from the original intention of ending in self memory. Hu Shi was happy to mail his diary of notes to Xu Yisun and other domestic friends to invite friends to make a biography, and urged them to publish it in New Youth