The effect of low temperature, drought, low temperature plus drought on maize growth was imitated in phytotron. The effect of low temperature, drought, low temperature plus drought on the physiological process of maize in the seedling and the heading stage is quantitatively evaluated. The result shows that low temperature and drought stress had negative effect on physiological process and the negative effect was enlarged while low temperature plus drought. A evaluation equation of the effect of the stresses on grain yield is as: y=516.2162+58.72343x₁+125.9081x₂+114.8233x₃. Where, y is the grain yield (kg·hm ^-2), x₁ is the soil humidity (%), x₂ is the air temperature at seedling stage (℃) and x₃ is the air temperature in the heading stage(℃).