The dynamic variation of ultraweak luminescence(UWL) and photosynthetic characteristics, and their relationship under drought stress of 20% PEG treatment and drought stress with regulating of reactive oxygen by carrying out four treatments of PEG, PEG + hydrogen peroxide (H₂O₂), PEG+ sodium benzoate and distilled water (CK) in Sedum hybridum seedling to supply theoretical basis for understanding the generation of UWL. The results showed:（1） in process of drought stress by PEG treatment, net photosynthesis (P_n), transpiration rate (T_r), intercellular CO₂ concentration (C_i), stomatal conductance (G_s), chlorophyll a (Chla), chlorophyll b (Chlb), chlorophyll (Chl) and UWL intensity all decreased; above photosynthetic characteristics and UWL intensity of PEG treatment decreased more quickly and had a bigger drop.（2） In drought stress with regulating by H2O₂ and sodium benzoate, P_n, T_r, G_s, C_i, Chla, Chlb,Chl and UWL intensity of treatments of PEG+ H₂O₂ and PEG+ sodium benzoate all decreased along with stress time as well as PEG treatment. However, above photosynthetic characteristics and UWL intensity of PEG+ H₂O₂ were lower than those of PEG treatment, while above photosynthetic characteristics and UWL intensity of PEG+ sodium benzoate were higher than those of PEG treatment. The results indicated that sodium benzoate treatment played the role of relieving drought stress and increasing UWL intensity.（3） Correlation analysis showed UWL intensity was positively correlated with photosynthetic index under drought stress and drought stress with regulating of reactive oxygen. In conclusion, under drought stress and drought stress with regulating, photosynthesis parameters decreased more quickly than that of CK, UWL intensity decreased more quickly than that of CK too; UWL intensity decreased along with the decline of photosynthetic efficiency.Which stated that the generation of UWL in plants positively related to extent of photosynthesis of plants, UWL intensity reflected the extent of adversity stress in plants.