Book Er refers to the disaster in the history of China, which resulted in a large number of books being lost and incomplete. In ancient times, officials collected books, which were called "Book moths". Sui Niuhong put forward "Five Harms", and Hu Yinglin added "Five Harms" in Ming Dynasty: Qin Shihuang's book burning, Wang Mang's rebellion, Dong Zhuo's disaster, Eight Kings' rebellion in Western Jin Dynasty, Hou Jing's rebellion, Zhou Shi's invasion, melee at the end of Sui Dynasty, Tang Anshi's rebellion, war at the end of Tang Dynasty, Jingkang's disaster in Northern Song Dynasty and Shaoxing's disaster in Southern Song Dynasty. Ten years later, the scattered death in Ming and Qing dynasties became more serious.