Abstract:The effects of biochar on physiological characteristics of cucumber seedlings in DBP contaminated soil were studied through simulation experiments. Four biochar treatments (CK, C 0.5%, C 1% and C 2%) and three DBP concentration gradients (0,20 and 40 mg/kg) were designed. The results showed that when the biochar was applied to DBP contaminated soil, the stability of cell membrane was enhanced at low concentration (C 0.5%), and remained basically the same as that of CK at high concentration (C 1% and C 2%). The application of biochar significantly enhanced SOD activity in cucumber seedlings, reduced CAT activity and content of photosynthetic pigment (chlorophyll a, chlorophyll b, chlorophyll a+b and carotenoid), but had no regular effect on APX activity, and C 2% treatment significantly increased POD activity. C 0.5% treatment significantly decreased Fsub>0, Fm and Fv/Fm. ΦPSⅡ decreased at low concentration (C 0.5%), and remained basically the same as that of CK at high concentration (C 1% and C 2%). When the biochar was 0.5% (C 5%) and DBP was 0 mg/kg, qP was the largest. The effect of applying biochar on NPQ was the most significant in C 1%. Grey correlation analysis showed that the effects of biochar and DBP on cucumber seedlings were firstly reflected in the activities of main antioxidant enzyme, then the chlorophyll fluorescence system changed accordingly, and finally the stability of cell membrane and the change of photosynthetic pigments content were affected. The results could provide scientific basis for further research on biological characteristics of facility crops, DBP pollution control and reasonable application of biochar.