The invention provides a medical composition. The medical composition comprises n-Butylidenephthalide (Type Z) illustrated by formula (I) and used for effective dose treatment, type E or the mixture of type E and type Z, or medically acceptable salt or ester and a medically acceptable carrier. The medical composition in the invention can be used for treating liver injuries such as liver fibrosis, liver cirrhosis and liver abscess, and/or improving liver functions.