Abstract: This research aimed to investigate the apoptotic effect of rhein on human primary liver cells(L-02)and the underlying mechanisms. MTT assay was used to detect the inhibitory activity of rhein on L-02 cells. Rhein-induced apoptosis in L-02 cells was evaluated by flow cytometry. Intracellular reactive oxygen species(ROS)was detected by DCFH-DA fluorescent probe. Endoplasmic reticulum stress-related gene and protein expression were detected by real-time quantitative PCR(RT-qPCR)and Western blot. The effect of antioxidant N-acetylcysteine(NAC)on these proteins, cysteinyl aspartate specific proteinase 4(caspase-4)and cysteinyl aspartate specific proteinase 3(caspase-3)activity was explored. The results showed that rhein inhibited the viability of L-02 cells in a dose-dependent and time-dependent manners. The apoptosis rate of L-02 cells in rhein-treated groups was increased significantly. Rhein induced generation of ROS which was blocked by NAC. The expressions of GRP 78, ATF-4, CHOP mRNA and the expressions of GRP 78, p-JNK, CHOP proteins were significantly increased in rhein-treated groups. However, NAC could not attenuate the expressions of GRP 78, p-JNK, CHOP proteins, caspase-4, caspase-3 activity induced by rhein significantly. In conclusion, rhein induces apoptosis in L-02 cells via a reactive oxygen species-independent endoplasmic reticulum stress pathway.