Objective: To study the antioxidation activities in vitro of a comment flavonoid component named vicenin Ⅱ(Apigenin 6,8-di-C-glucoside) in Dendrobii Officinalis Caulis from different origin places and investigate its effects on apoptosis of HepG2 cells. Method: The antioxidation activities in vitro of vicenin Ⅱ (0.005-1 g·L^-1) were evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH), salicylic acid and 2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid(ABTS) and copper ion reduction assays. Methye thiazolye telrazlium(MTT) assay was used to test the inhibitory effect of vicenin Ⅱ(12.5~100 μmol·L^-1) on proliferation of 6 tumour cells in vitro. In subsequent apoptosis experiment, the concentration of vicenin Ⅱ was 75 μmol·L^-1. The morphological changes of HepG2 cells were evaluated by Hoechst 33258 under fluorescence microscope; and the cell apoptosis rate was detected by flow cytometry with AnnexinV/PI apoptosis assay kit. The mRNA expressions of mitogen activated protein kinase (MAPK) pathway related apoptotic genes were detected by Real-time PCR assay. Result: The 1 g·L^-1 vicenin Ⅱ showed 48.82% and 22.01% for DPPH scavenging rate and Cu²⁺ reduction rate respectively(P<0.01). 0.5 g·L^-1 vicenin Ⅱ showed 86.88% for ABTS scavenging rate(P<0.01). vicenin Ⅱ could significantly inhibit the proliferation and increase the apoptosis rate on HepG2 cells; after treatment for 48 h with 75 μmol·L^-1 Vicenin Ⅱ, the cells survival rate was 45.69%(P<0.01) and apoptotic rate was 14.57%(P<0.01). Meanwhile, the mRNA expression levels of B-cell lymphoma-2 (Bcl-2) related X protein (Bax)/Bcl-2, Caspase-8, p38, extracellular signal-regulated kinases (ERK), c-Jun N-terminal kinase (JNK), and nuclear transcription factor (NF)-κB were increased(P<0.01). Conclusion: The general flavone glycosides component vicenin Ⅱ of Dendrobii Officinalis Caulis from different origins has a certain antioxidation effect and significant inhibitory effect on proliferation, and could induce apoptosis on HepG2 cells probably by regulating the expression of related genes in MAPK pathway and Bax/Bcl-2.