Abstract: Maize cultivar Shandan 609 was used to determine the effects of drought stress on photosystemⅡ, dry matter accumulation, protective enzyme activity and
  proline content at seedling stage in pot experiment. Two drought treatments (moderate drought and severe drought) were tested. The results showed that dry matter accumulation, leaf area and plant height of cultivar shaandan 609 decreased significantly with the increasing  drought stress. The less grouped PSⅡunits (L_band>0), severely damaged OEC (K_band>0), and the inhibited acceptor side (Ψ_o significantly decreased) resulted in the overall dropped performance of PSⅡ (PI-ABS). Under the condition of moderate and severe drought stress, the activities of superoxide, peroxidase, catalase and   proline content increased significantly, which were 1.3, 1.1, 1.2, 5.8 and 1.1, 3.3, 1.5, 15.0 times of control (CK), respectively. Those results indicated that damage of PSⅡ acceptor and donor side under drought stress led to the decline of PSⅡ performance, which was likely to cause the decline of dry mater accumulation of maize cultivar Shandan 609, while protective enzymes and proline as protective substance in plant played a positive role in drought resistance.