Abstract: Putting the 3rd—leaf stage seedling of late variety of corn, Jidan 159 in the low temperature of 6℃ and 10℃ to treat for 3 and 6 days, it is shown that the proline content is increased obviously, and the electric conductance is also raised. The content of solubility protein is increased firstly and then decreased with the prolongment of treatment time. The SPAD value of chlorophyll is decreased, and the photosynthetic rate is decreased.