The Book of the New Tang Dynasty contains the deeds of Zhang Xu, which is attached to the Biography of Li Bai. Zhang Xu's calligraphy is the beginner of Lu Yanyuan, the son of Lu Jianzhi. Zhang Xu served in the imperial court, served as an official in Chang 'an and Beijing, and met Yan Zhenqing and Du Fu.
Zhang Xu is famous for his drinking. In Du Fu's poem "Song of Eight Immortals Drinking", Zhang Xu is also one of the characters described, and he is called "Eight Immortals Drinking" together with others. Zhang Xu is famous for his most unrestrained cursive script in calligraphy. According to New Tang Book, Zhang Xu likes to write works after drinking, which is called "Crazy Grass". His calligraphy is mostly composed of grotesque shapes, exaggerated thickness contrast and emotional lines in series, which is known as "The Book of the Old Tang Dynasty". Zhang Xu's cursive script and Li Bai's poems, as well as Pei Min's sword dance, are collectively called the Three Musts. However, Zhang Xu not only wrote cursive script, but also was the grandson of another famous calligrapher in Tang Dynasty, Lu Jianzhi. He was also proficient in regular script and Chinese painting. According to legend, his Wild Grass was inspired by watching Gong Sundaniang and his disciples practice swords.
Before Zhang Xu, the calligraphy circle always took Wang Xizhi and Wang Xianzhi as the norms, but Zhang Xu's calligraphy broke this convention and brought a whirlwind change to the calligraphy circle. Du Fu wrote in the Song of the Eight Immortals: "Three cups of grass in Zhang Xu, with their hats off, appeared before the princes, like a cloud." It is said that Yan Zhenqing and Li are his disciples, which is unconfirmed. But Cui Biao and Yan Zhenqing are indeed Zhang Xu's disciples. Zhang's brushwork was published in the "Youxian Initiative" and passed on to Cui Biao and Yan Zhenqing. "Therefore, Zhenqing himself mentioned that he followed Zhang Xu to learn brushwork in Zhang Changshi's Twelve Meanings. Wu Tong is also a disciple of Zhang Xu.
There are many records about Zhang Xu in the Tang Dynasty. The most well-known one is that he even wrote with his hair when he was inspired by drinking. Zhang Xu's handed down works include Four-character Poems, Thousand-character Works, Langguan Shizhu Ji, Sad Autumn Fu, Abdominal Pain Post and so on. Among them, Four Ancient Poems includes two poems by Yu Xin and two poems by Xie Lingyun: Ode to the Prince, Ode to the Husband under the Rock and Ode to a Four-or Five-year-old Boy, with a total of 40 lines. Height 28.8 cm, width 192.3 cm, written on five-color paper. It is now in the Liaoning Provincial Museum in China. His works were loved by Li Ang when he was in Tang Wenzong, and were listed as one of the "Three Musts". At that time, Huai Su, a young calligrapher in the Tang Dynasty, was also good at cursive writing. He also loves writing after drinking, and there is a common name called "drunk".