Liu Gongquan came from Tang Muzong Dynasty. On one occasion, Mu Zong asked Liu Gongquan: "How can the green tree be so good?" Liu Gongquan replied: "Use a pen in your heart, and your heart is correct." Mu Zong looked serious and knew that Liu Gongquan wanted to use calligraphy to regulate himself. This matter was passed down as a "pen admonition" story by later generations. Liu Gongquan has a high character, not only a loyal minister, but also a dutiful son. At that time, the calligraphy collection of ministers or ministers' families was regarded as unfilial if there was no Liu Zi. Liu Gongquan (778-865), a native of Jingzhao Huayuan (now Yaoxian County, Shaanxi Province), was born sincere. Mu Zong, Jing Zong and Wenzong were forbidden to be calligraphers, and they were great calligraphers in the late Tang Dynasty. He is a beginner of the "two kings" and takes Yan Shu's meaning as his body. The book is charming, healthy, and keeps the bones and muscles in a unique way. Together with Yan Shu, it is called "Yan Liu Jin Gu".