This is the first study on peanut VDE, which led to multiple biochemical and physiological changes to heat and HI stress by improving de-epoxidation of the xanthophylls cycle. A peanut (Arachis hypogaea L.) violaxanthin de-epoxidase gene (AhVDE) was isolated by RT-PCR and RACE methods. The deduced amino acid sequence of AhVDE showed high identities with violaxanthin de-epoxidase of other plant species. The expression of AhVDE was obviously upregulated by 4, 40 °C and high light, NaCl, and abscisic acid. Sense and RNAi transgenic tobaccos were further used to investigate the physiological effects and functional mechanism of AhVDE. Compared with WT, the content of Z, the ratio of (A + Z)/(V + A + Z) and the non-photochemical quenching were higher in sense plants, and lower in the RNAi lines under heat and high irradiance (HI) stress, respectively. Additionally, photoinhibition of photosystem II (PSII) reflected by the maximal photochemical efficiency in WT lines was more severe, and in the RNAi lines was the most severe compared with that in the sense lines. Meanwhile, overexpressing AhVDE also led to multiple biochemical and physiological changes under heat and HI stress. Higher activities of superoxide dismutase and ascorbate peroxidase, lower content of reactive oxygen species and slighter membrane damage were observed in sense lines after heat and HI stress. These results suggested that, peanut VDE can alleviate PSII photoinhibition to heat and HI stress by improving the xanthophyll cycle-dependent energy dissipation.