Zhang Xu's calligraphy originated from "Two Kings", and his regular script was correct and rigorous. The rules are extreme, and Huang Gu is called "the first in the Tang Dynasty". But his regular script is more inheritance than creation, and there is nothing new.
His cursive script is a great innovation and development of calligraphy. Han Yu said, "Xu is good at cursive writing, but he can't cure his book." Change is like ghosts and gods, so don't be arrogant. " Du Fu wrote in Song of the Eight Immortals: "Zhang Xu's three cups of grass are sacred. He waved his paper like a cloud before taking off his hat to reveal the top of the maharaja. " He can sublimate the art of calligraphy to the artistic realm of expressing calligraphers' thoughts and feelings with abstract points and lines. In the art of calligraphy, his handwriting seems strange but not strange. The key is that the pen for stippling completely conforms to the traditional rules. It can be said that he used traditional techniques to express his personality and became a creative calligrapher worthy of his own time in calligraphy. Broad, fresh and unrestrained, far more than the previous calligraphers' works, with a strong flavor of the prosperous Tang Dynasty.