Based on the ancient literatures

the origin and formation of the theory of Four Qi in Chinese Medicines were discussed. Under the influence of the philosophy of "correspondence between man and nature"

the ancient people introduced cold

heat

warmth

coolness

clearness

sorrow

and other terms that describe climate into medicine to explain the etiology and pathogenesis

and to indicate the rule of treatment

etc. The basis for distinguishing the principle of cold and heat treatment is closely related to the theory of Yin and Yang; the medicines are classified into different properties such as "hard medicine"

"soft medicine"

"yin medicine"

and "yang medicine" etc. Although they are not named as cold and heat medicines

they have the property of cold and heat medicines. In fact

with the help of Yin-Yang theory′s extensive application in syndrome differentiation

principle

and treatment

the "Four Qi" describing in the climate of the four seasons are summarized as the cold and heat properties of the drug

so as to indicate the functional mechanism of the drug. Therefore

it is believed that the essence of the Four Qi theory of Chinese Medicines is to balance the yin and yang unbalance of the body. Based on the efficacy and usage

the degree of coldness and heat of the drug was divided.