Abstract: The effects of Cd stress on the physiological characteristics of maize were studied. The results show that when maize grows normally, the resistance of maize against Cd is strong. The indexes of chlorophyll content and peroxide enzyme increase firstly at 0.2mg／L, 0.5mg／L, 1.0mg／L of Cd. The maximum stimulating concentration of Cd is 1.0mg／L and the toxicity concentration is 5.0mg／L. With the prolong of time and accumulation of Cd, the chlorophyll content decreases gradually, the activity of root falls and resumes, and the free proline increases and drops, indicating that the resistance of maize is strong and the poisons of Cd is restricted by the factors of time and its concentration. The dissociate proline changes obviously, it may be as a guide line of some plants against heavy metal.