Transgenic tobacco plants with 2–Cys Prx (Longjiang911) was chosen to investigate the photochemical activity of transgenic tobacco plants under drought stress. The results showed that the relative fluorescence intensity in K and J point of OJIP curve in leaves of the transgenic tobacco plants with 2–Cys Prx were lower than those of the non transgenic tobacco (CK) under drought stress, but opening degree of surplus active reaction center (Ψo) at 2 ms was significantly higher than that of CK. Improved 2–Cys Prx expression could increase the photocatalytic activity of OEC in PSⅡ electron donor and the electron transport from QA to QB in acceptor side under drought stress. The electron transport chain beyond QA– (φEo) in leaves of the transgenic tobacco plants with 2–Cys Prx were higher compared to the CK, but best quantum yield of non-photochemical quenching (φDo) were less compared to the CK. 2–Cys Prx could increase drought-resistant ability of the transgenic tobacco plants by improving photochemical activity and changing absorbed light allocation in leaves of tobacco seedlings.