Zhang Xu in Tang Dynasty and Huai Su in Middle Tang Dynasty were the pioneers of cursive script in Tang Dynasty. Zhang Xu's cursive script, which inherited the two kings and traced back to Zhang Zhi, has obvious originality. His books are unrestrained and uninhibited, and the vertical pen falls like a rabbit, which has the trend of "sudden rain and sudden wind". In addition, his most affectionate deeds, such as Du Fu's poem, said: "Zhang Xu handed down three cups of grass, took off his hat and exposed the top of the princes, waving paper like a cloud", which was called "Zhang Dian" in the world and "Crazy Grass" in his cursive script, which was a new expression of grass in the Tang Dynasty. Huai Su, who was later than Zhang Xu, got Zhang Xu's cursive script from Yan Zhenqing. His cursive script is like the wind, fantastic, smart, elegant and natural, and his pen has the trend of "the wind tends to rush electricity", which is called "crazy element" internationally. Historically, they have been called "crazy elements". Huang Tingjian commented: "These two people are the champions of a generation of cursive scripts." Zhang Xu and Huai Su's achievements in cursive writing were affirmed.