Zi Yuan is a kind of traditional Chinese medicine, which belongs to the antitussive and antiasthmatic drugs in traditional Chinese medicine. It is the dried root and rhizome of the plant Aster. Meridian tropism belongs to lung meridian. Warm in nature and bitter in taste. It has the effects of moistening lung, lowering qi, resolving phlegm and relieving cough.

Clinically, it is often used for cough with excessive phlegm, old and new cough. Phlegm can be used regardless of exogenous cold or internal injury. Excessive phlegm and cough caused by exogenous pathogens are often raw. If it is because of lung deficiency or internal injury, Aster honey is often used.

Aster is also commonly used in modern medicine. Mainly used for acute bronchitis and acute pneumonia, such as chronic obstructive pulmonary disease and tuberculosis. Zi Yuan can be used as medicine.