Zhang Xu's calligraphy began with Zhangzhi and Erwang, with cursive script as the highest achievement. He himself is proud of inheriting the tradition of "two kings" and writes very well. On the other hand, he imitated Zhang Zhi's cursive art and created an unpredictable wild grass, which shocked the world. According to legend, he saw the princess arguing with her husband, and he heard the advocacy and got the meaning of brushwork; When I was in Yexian County, Henan Province, I loved watching Gong Sundaniang dance the sword of Xihe River, so I got the grass god. Yan Zhenqing resigned twice and asked him for his brushwork. Zhang Xu is a pure artist. He pours his emotions into stippling, and no one looks at it, and he is as intoxicated as a madman. Tang Hanyu praised in "Preface to Send a Noble Sage to a Master": "Emotion, embarrassment, sadness, happiness, resentment, longing, drunkenness, boredom and injustice, if moving in the heart, must be expressed in cursive script. Looking at things, we can see mountains and rivers, cliffs and canyons, birds, animals, insects, fish and flowers, the sun, the moon and stars, storms and fires, lightning and thunder, singing and dancing battles, and changes in heaven and earth. Congratulations, one is in one book, so the book of Xu is still as unpredictable as ghosts and gods, and it will eventually be praised by later generations. " This is a true portrayal of a real artist's obsession with art. No wonder later generations talked about calligraphy in the Tang Dynasty, and praised Europe, Yu, Chu, Yan, Liu and Su, but they all praised Zhang Xu, which is unique in the history of art.
There are "Stomach Pain Sticks" and "Four-character Poems" handed down from ancient times.