Transgenic tobacco plants(Longjiang911) with 2–Cys Prx overexpressed and suppressed were chosen to investigate their growth characteristics and photochemical activity. The results showed that plant height, root length, biomass in transgenic tobacco plant with 2–Cys Prx overexpressed were significantly higher than those in the non transgenic tobacco (CK); electron transport rate (ETR) of transgenic tobacco plants with 2–Cys Prx expression suppressed was significantly lower than that of the plant with 2–Cys Prx overexpressed. Area within OJIP curve and Fm, opening degree of active reaction center (Ψo) at 2 ms, quantum yield of electron transport (φEo) after absorbed Photoenergy used in QA, electron transport flux per reaction center (ETo/RC) in leaves of transgenic tobacco plant with 2–Cys Prx overexpressed were lower than those in the CK, while in leaves of transgenic tobacco plant with 2–Cys Prx suppressed were higher than those in the CK. Maximun quantum yield (φDo) from non-photochemical quenching, dissipated energy flux per reaction center (DIo/RC) in transgenic tobacco plant with 2–Cys Prx overexpressed were lower than those of CK, whereas in transgenic tobacco plant with 2–Cys Prx suppressed higher than those of the CK. In leaves of transgenic tobacco plant with 2–Cys Prx overexpressed, more absorbed light energy were inclined to allocate to photochemical reaction, while the dissipated energy in invalid form decreased, which facilitated the supply of assimilation force for carbon assimilation. In leaves of transgenic tobacco plant with 2–Cys Prx suppressed, the ratio of absorbed light energy for photochemical reaction was relatively reduced.