The concept of god was an important category in Zhang Zai's philosophy and was built on the basis of his analyzing "zhou yi"."The change of can wu" in "Zhouyi"was really hard to understand, so Zhang Zai made some explanations to it in his works "Heng Qu Yi Shuo".He thought that "the change of can wu" was a kind of "divine change of can wu".According to him, "the change of can wu" mainly reflected"the combination of dynamics and statics" and "eventuality of yin and yang".