: 11-Oxo-mogroside V is a natural sweetener, exhibits strong antioxidant activity. It exhibits significant inhibitory effects on reactive oxygen species (O2-, H2O2 and *OH) with EC50 of 4.79, 16.52, and 146.17 μg/mL, respectively. 11-Oxo-mogroside V exhibits the remarkable inhibitory effect on two-stage carcinogenesis test of mouse skin tumor induced by 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a promoter.