【Abstract】Objective To study the effect of cucurbitacin E (CuE) on apoptosis of human colonic cancer HT29 cells induced by endoplasmic reticulum stress(ERS) and autophagy in vitro. Methods The cultured HT29 cells were treated with CuE at 0001, 001, 01, 1 and 10μmol/L for 24, 48 and 72 hours, respectively. The changes of cell apoptosis were detected by flow cytometry coupled with Annexin VFITC/PI staining. The Western blot assay was used to detect the protein expression of CHOP, Grp78, Beclin1 and LC3. Results The results of flow cytometry coupled with Annexin VFITC/PI staining revealed that with the increase of CuE concentration. The proportion of apoptotic cells and total cells was increased significantly. Western blot analysis showed that after treating HT29 cells with CuE for 24 hours. The expression of endoplasmic reticulum stressrelated proteins CHOP and Grp78 was significantly increased (P＜005). The autophagyrelated protein expression of Beclin1 was increased. The cytoplasmic type LC3 (LC3I) had an enzymatic hydrolysis, which was transformed into autophagy film type LC3II. The ratio of LC3Ⅱ/LC3I was decreased (P＜005) and then decreased (P＞005). Conclusion ERS and autophagy were involved in the apoptosis of human colon cancer cell line HT29 induced by CuE, which suggested that were an important pathway of colon cancer cell apoptosis induced by CuE.