Objects : Apoptosis leads to the death of a cell. The mitochondrial pathway of apoptosis, a process regulated by the Bcl-2 family of proteins, plays a key role in various biological processes. The tuber of Liriope platyphylla Wang et TANG (Liliaceae), also known as Liriopis tuber, is famous in Oriental medicine owing to its tonic, antitussive, expectorant and anti-asthmatic properties. The purpose of this study was to observe the effect of the Liriopis tuber on mitochondrial-mediated apoptosis in PC-12 cells. Method : A cytotoxic test on Liriopis Tuber water extract was conducted and another MTT assay was conducted to observe the cytoprotective effect against 4-HNE 25 ${mu}M$ that causes oxidative stress in PC-12 cells for 24 hours. In addition, in order to observe the expression of Bcl-2 and Bax protein involved with apoptosis, western blot was conducted. Results : The LT water extract had no toxicity for PC-12 cell. In the cytoprotective effect against 4-HNE, both of the group treated with 50 ${mu}g/m{ell}$ and 100 ${mu}g/m{ell}$ of LT water extract showed a significant increase in comparison with the control group. In Bax protein expression, all the experimental groups treated with LT water extract showed a decrease in comparison with the control group but had no significance. In Bcl-2 protein expression, all the experimental groups treated with LT water extract showed a significant increase in comparison with the control group. Conclusion : These results suggest that LT is effective in reducing apoptosis.