The violaxanthin cycle (V-cycle),reversible conversion of violaxanthin (V) to zeaxanthin (Z) via the intermediate antheraxanthin (A),is a reversible switch of photosynthetic light-harvesting complexes between a light-harvesting state under low light and a dissipative state under high light.Xanthophylls such as zeaxanthin are known to play a crucial role in deactivating triplet chlorophyll (³Chl^*) and singlet oxygen (¹O₂^*).Violaxanthin cycle is further assumed to be involved either directly or indirectly in the non-photochemical quenching (NPQ) of excess light energy in the antenna of PSⅡ.Binding of xanthophylls by antenna proteins of both photosystems is essential to the regulation and function of the V-cycle.Because antenna proteins bind the substrates,V and Z,of the two Vx-cycle enzymes,VDE and ZEP,respectively,and antenna proteins are supposed to be the site for the Z-dependent dissipation of excess light energy.The lipid properties of the thylakoid membrane have a strong impact on xanthophyll conversion.The kinetics of violaxanthin de-epoxidation is likely to be limited by xanthophyll diffusion within the membrane.This assumption is supported by the fact that the first step of de-epoxidation (the V to A conversion) exhibits a 4～6 times higher rate constant than the second step (the A to Z conversion).The current knowledge supports the view that antenna proteins and thylakoid membrane lipids are essential modulators of violaxanthin cycle.Here a review is given on recent progress in the biochemical reaction and photoprotective functions of xanthophylls,structural properties of xanthophyll-cycle enzyme and cofactors,the regulation of xanthophyll cycle by antenna proteins and thylakoid membrane lipids.