During the change of Han and Wei Dynasties, warlords fought and the people were miserable, so during the Jian 'an period of Emperor Xian of Han Dynasty (196 ~ 220), a number of "Three Caos" (Cao Cao, Cao Pi and Cao Zhi) and "Seven Sons" (Kong Rong, RoyceWong, Chen Lin, Liu Zhen, Xu Gan, Ruan Yu and Angelababy) were produced. The characteristics and background of Jian 'an style are just as commented in Wen Xin Diao Long Time Series: "When you look at the time of writing, it is elegant and generous, good things are scattered in the world, the wind is declining and vulgar, and the ambition is deep and the pen is long, so the outline is rich and angry." For example, Cao Cao (155 ~ 220:) wrote a crusade against Yuan Shao in Hao and a crusade in A Journey to Bitter Cold, all of which described the course of events, the cruelty of war and the sufferings of the people, and were praised by later generations as "the true record of the end of Han Dynasty and the truth of the history of poetry" (Zhong Xing's "Ancient Poems Return"). Cao Cao's short songs, Jiao Shushou, Cao Zhi's White Horse Wang Biao, Miscellaneous Poems, etc. They all express the author's true and complicated thoughts and feelings, and are worthy of being excellent works of expressing feelings and aspirations. Especially, White Horse Wang Biao by Cao Zhi (192 ~ 232) analyzes the grief and indignation in the cruel struggle within the royal family, which is a masterpiece combining realism with lyricism. Cao Zhi is especially good at five-character poems. On the basis of Cao Cao's elegance, he paid more attention to "excellent words" and "gorgeous", thus making the five-character poems more prosperous. Ge Yanxing written by Cao Pi (187 ~ 226) is the first complete seven-character poem written by literati in history.