Radix Angelica sinensis, known as Danggui and mainly spread in Gansu and Sichuan provinces of China, has been used for a long time as a traditional Chinese medicine to treat cardiovascular and cerebrovascular diseases (1, 2) as well as a common food supplement to reinforce vital energy (3, 4). Modern phytochemical studies have shown that LIG (Fig. 1) is the main lipophilic component of Danggui (1). Our previous studies have shown that LIG had neuroprotective effects on some models of diseases associated with cerebral ischemia. Treatment with LIG could significantly improve behavioral deficits and dose-dependently reduce cerebral infarct volumes after focal cerebral ischemia in rats (1, 5). It could also prevent chronically hypoperfused cognitive deficits and brain damage in rats induced by permanent ligation of both common carotid arteries (6). A recent study has shown that LIG has a neuroprotective effect on Alzheimer's disease, cognitive impairment and neuropathological changes induced by bilateral intracerebroven- To improve the stability and oral bioavailability of Z-ligustilide (LIG), the inclusion complex of LIG with hydroxypropyl-b-cyclodextrin (HP-b-CD) was prepared by the kneading method and characterized by UV-Vis spectroscopy, differential thermal analysis (DTA) and Fourier transform infrared (FTIR) spectroscopy. LIG is capable of forming an inclusion complex with HP-b-CD and the stoichiometry of the complex was 1:1. Stability of the inclusion complex against temperature and light was greatly enhanced compared to that of free LIG. Further, oral bioavailability of LIG and the inclusion complex in rats were studied and the plasma drug concentration-time curves fitted well with the non-compartment model to estimate the absolute bioavailability, which was 7.5 and 35.9 %, respectively. In conclusion, these results show that LIG/HP-b-CD complexation can be of great use for increasing the stability and biological efficacy of LIG.