The mutual hiding of the five elements is a useful principle

with five elements participating in infinite interactions. As an important part of the theory of the five elements

mutual hiding of the five elements explains the relationship among these elements from multiple perspectives

which is the internal basis of generation and restriction relationship among the five elements and the basic condition for maintaining the dynamic balance of the four qi movements with the middle earth as its pivot. However

at present

the theory of mutual hiding of the five elements has not attracted enough attention

and the related research has not yet formed a foundational understanding of this theory. Therefore

based on the notion of "qi-yin and yang-five elements"

this paper introduces a further discussion on the theory of mutual hiding of five elements and argues that any one of the five elements contains five qi and that any one of the five qi is present in all five elements. This paper then proposes the law of the growth and decline of the five elements in mutual hiding

including "si (beginning)" "xiang (developing)" "wang (prosperous)" "xiu (waning)" "qiu (disappearing)"

explores and analyses the primary and secondary relation among five qi of each element space-time unity nature of the theory so as to improve it and use it effectively in clinical practice.