Abstract: In order to clarify the response rules of photosynthetic and physiological characteristics of Yulania stellata to flooding stress,the double-pot method was used to Y.stellata and its 4 cultivars by flooding.Thechanges in chlorophyll content,specific leaf area,photosynthetic parameters and chlorophyll fluorescenceparameters after different flooded days were measured respectively.The results showed that the changing trendsof chlorophyll a,chlorophyll b and total chlorophyll were slightly different under flooding stress,and there wereno significant changes in Y.’（Mag’s）Piroutte’ and Y.stellata ’Chrysanthemiflora’,while Y.’Bety’,Y.stellata and Y.’Judy’showed a downward trend respectively.The net photosynthetic rate（P_n）showed a downwardtrend,and the maximum net photosynthetic rate(P_nmax)and light saturation point（LCP）of the treatment groupswere significantly lower than those of the control group respectively.The dark respiration rate（R_d）of Y.stellata’Chrysanthemiflora’and Y.’（Mag’s）Piroutte’of the treatment group was higher than that of the control group.The Rd of Y.’Bety’,Y.stellata and Y.’Judy’were significantly reduced after flooding treatment to reduce theconsumption of photosynthetic products respectively.The effective photochemical quantum yields(Φ_PSⅡ)of Y.’（Mag’s）Piroutte’and Y.’Judy’decreased by 8.4% and 24.7% under flooding stress;Y.stellata’Chrysanthemiflora’,Y.’Bety’and Y.stellata decreased significantly,respectively 76.7%,85.7% and 64.6%.The maximum photochemical quantum yield（F_v/F_m）of each cultivar of Y.stellata.had a downward trend.Thephotosynthetic characteristics of Y.stellata and its cultivars were affected by flooding stress,but differentcultivars had differences.Except for Y.’Bety’,the Photosynthesis of the other 4 Y.stellata cultivars performednormally during the 7 d before treatment;Y.’（Mag’s）Piroutte’had strong photosynthetic capacity andwaterlogging adaptability.The results provid a theoretical basis for the selection of Y.stellata cultivars suitablefor planting in wet and waterlogged areas in southern China.