Abstract: Abstract：[Objective] To study the low temperature stress on wheat, corn, radish seedlings and SOD activity of three plants affected by the degree of difference. [Method] With the radish, maize, wheat seedlings as tested materials, determine SOD activity by NBT autoxidation method, from the stress of temperature changes and stress time changes study low temperature stress on wheat, corn, radish seedlings SOD activity by the test method of simulated low temperature damage. [Results] As the temperature decreased, SOD activity of wheat, corn, radish seedlings was increased at first, then have shown a downward trend, and 0℃ activity of the enzyme is lower than the group grown at 25℃; with the stress time change, the SOD activity of wheat, corn , radish seedlings of different movements, but the 0℃ stress, little change in activity, and lower than the normal temperature group activity. [Conclusion] The appropriate low-temperature processing can enhance the SOD activity, beyond the scope of plant’s tolerance, the activity was inhibited and decreased.