The development of kuang cao, or wild cursive calligraphy style, was another important achievement of the Tang Dynasty in calligraphy ZhangXu and Huai Su are its two leading representatives.

Zhang Xu was a native of Wujun (present-day Suzhou in Jiangsu Province). He had served as a regional officer, liked to drink and indulged fully in life's pleasures. He usually wrote for enjoyment after drinking, at the same time shouting and walking about. Records show he soaked his own hair with ink and used it to create a calligraphy work, thus earning himself the nickname "Crazy" Zhang.

Zhang Xu's kuang cao calligraphy shows much diversity. According to a modern scholar, Han Yutao, Zhang's calligraphy works have three properties. First, they were wild. He always finished a calligraphic work in one sweep and, consequently, when reading his calligraphy work, one can feel the momentum. Second, they were strange and always varied. Zhang's calligraphy is as unpredictable as his brushstrokes and character structures are unfathomable. Third, they were formidable. Previous Chinese calligraphic works had a slender beauty, while the calligraphy work of Zhang Xu makes the reader feel as if one's head were pressed down by stones. Reading Zhang-s calligraphy, one has the feeling of being threatened by a sword, yet one respects his dignity. Though Zhang Xu's kuang cao were wild and crazy, his brushstroke technique adhered to certain rules, and he was also proficient at the more restrained kai calligraphy. only a few of Zhang Xu's works have remained to this day. The ones we can find now are his Dutong Tie (Stomach Ache Calligraphy Copybook) and Gushi Si Tie (Four Poem Calligraphy Copybook).(Fig.1-12)

The other great kuang cao calligrapher of the Tang Dynasty was Huai Su, a native of Tanzhou (present-day Changsha, Henan Province). He became a monk in his childhood. He was more than 20 years younger than Zhang Xu and learned from Zhang Xu's and Yan Zhenqing's work. He studied calligraphy diligently while a child, and his style was mannerly and bold. The famous Tang Dynasty poets Li Bai and Qian Qi spoke highly of his calligraphy works. Compared with Zhang Xu's calligraphy, Huai Su's strokes are much thinner(Fig.1-13)

In ancient books on calligraphy, Chinese men of letters liked to depict the various calligraphic styles as metaphors for natural scenery or phenomena. An appreciation and understanding of Chinese calligraphy require rich life experience. Chinese calligraphy, especially kuang cao, is a mysterious art. Most kuang cao writers were full of passion when they created their works. In appreciating a calligrapher's work, readers feel the artist's mood, a reaction that is a most important characteristic of expressionist art. In the Tang Dynasty, the dominant painting style was gongbi zhongcai, which was highly realistic with exact delineation and enriched colors. It was a judicious painting method that took a long time to execute and was constrained by the shapes of the subject. As a result, it left little room for painters to reveal their own thoughts. It was against this background that kuang cao flourished in the Tang Dynasty since, in calligraphy, the writer could fully express his emotions.

There were many great kuang cao calligraphers in later dynasties, Such as Huang Tingjian of the Song Dynasty, Zhu Yunming, Xu Wei and Wang Duo of the Ming Dynasty, Fu Shan of the Qing Dynasty and Lin Sanzhi of modern times. Each of them learned from their predecessors but formed their own distinctive qualities in their work.