To study the underlying mechanism of 20 (S)-Ginsenoside-Rh2 and 20 (R)-Ginsenoside-Rh2 inducing apoptosis of human lung adenocarcinoma A549 cells. In this study, cell death rate and cell survival rate were obtained using typan blue staining cell viability assay, and transmission electron microscopy was used to detect cell apoptosis. Meanwhile, IkappaB phosphorylation expression was analysed by western blotting. Results showed that after A549 cells were treated with 30 μg/mL 20(S)-Rh2 and 20(R)-Rh2 for 48h, cell death rate increased significantly compared with the control group (P<0.05), and nuclear condensation, fragmentation, karyopycnosis and apoptotic bodies were found under transmission electron microscope. There were no significant changes of IkappaB expression after treated with 20(S)-Rh2 and 20(R)-Rh2 (P>0.05). After treated with 20(R)-Rh2, p-IkappaB expression increased obviously between 4h-6h (P<0.05). After treated with 20(S)-Rh2, p-IkappaB expression increased obviously between 1h-2h (P<0.05), back to normal over time after 3h, increased significantly again between 4h-6h (P<0.05), which indicated the activation of IkappaB participated in A549 cell apoptosis induced by Rh2. These results demonstrated that 20(S)-Rh2 and 20(R)-Rh2 both have the functions of activating I-kappaB/NF-kappaB signaling pathway, thus promoting A549 cell apoptosis.