The famous calligrapher who uses a brush as a pen and yellow mud as ink to practice calligraphy is Yan Zhenqing. Yan Zhenqing has exquisite calligraphy and is good at running and regular script. He first studied under Chu Suiliang, and later under Zhang Xu, acquiring his brushwork. His regular script is dignified and majestic, and his running script is powerful. He created the "Yan style" regular script and had a great influence on later generations. Together with Zhao Mengfu, Liu Gongquan and Ouyang Xun, they are known as the "Four Masters of Regular Script". It is also called "Yan Liu" together with Liu Gongquan, and is also known as "Yan Jin Liu Gu".

Yan Zhenqing (709-August 23, 784), courtesy name Qingchen, nicknamed Xianmenzi, nicknamed Yingfang, was born in Jingzhao Wannian (now Xi'an City, Shaanxi Province), and his ancestral home is Langya. Linyi (now Linyi City, Shandong Province). A famous official and calligrapher of the Tang Dynasty, he was the grandson of the fifth generation of Secretary Yan Shigu and the younger brother of Situ Yan Gaoqing.

Yan Zhenqing was born in the Yan family of Langya. He became a Jinshi in the 22nd year of Kaiyuan (734) of Emperor Xuanzong of the Tang Dynasty, and served successively as the censor and censor. Later, because he offended the powerful minister Yang Guozhong, he was demoted to the prefect of Pingyuan, and was known as "Yan Pingyuan" in the world. During the Anshi Rebellion, Yan Zhenqing led the rebel army to fight against the rebels and regained Hebei for a time. Later he went to Fengxiang and was awarded the title of Minister of Xianbu. During the Tang Dynasty, he became the Minister of the Ministry of Personnel, the Crown Prince and the Grand Master, and was granted the title of Duke of Lu County, and was known as "Gong Yan Lu". In the first year of Xingyuan (784), he was sent to tell the rebel general Li Xilie, but he resisted the rebels sternly and was eventually hanged. After he was killed, his successor King Li Gao and the soldiers of the three armies all cried bitterly for him. Situ was given a posthumous title of "Wenzhong".