Abstract: The ecophysiological characteristics and photosynthesis of Humulus scandens seedlings under chromium stress (0,50,200,300,and 500 mmol/L Cr³⁺) were studied. Under 50 mmol/L stress,the net photosynthetic rate (Pn) and instant water use efficiency (WUE) increased significantly compared with the CK butstomatal conductance (G_s),transpiration rate (T_r),stomatal limitation (L_s),intercellular CO₂ concentration (C_i) and chlorophyll contents were not significantly different. Under 200-300 mmol/L stress,actual maximal fluorescence (F_m'),actual minimum fluorescence (F_o'),dark fluorescence yield (F_o),maximal fluorescence yield (F_m),variable fluorescence (F_v),potential activity of PSⅡ(F_v/F_o),maximum quantum yield of PSⅡ(F_v/F_m) and proportion yield of PSⅡ(qP) gradually decreased with an increase of Cr³⁺ stress,while L_s and WUE_i initially increased but then decreased,whereas C_i initially decreased but then increased. The opposite side of electron transport rate (E_TR) and malonaldehyde (MDA) showed a tendency to increase,while the coefficient of non-photochemical quenching (qN) showed irregular changes. In particular,the P_n,T_r,L_s,WUE_i,content of MDA and qN declined significantly in 500 mmol/L Cr³⁺ stress,but the C_i and other chlorophyll fluorescence parameters suddenly increased. In summer,there was a clear difference of gas change,content of MDA and chlorophyll and chlorophyll fluorescence parameters. Although some physiological indexes declined in the H. scandens seedlings with increasing Cr³⁺ stress,but showed a positive response,keep certain photosynthesis under high Cr³⁺ stress,and its tolerance to Cr³⁺ stress was the strongest.