Abstract: The mechanism of increased yield and sucrose content of sugarcane sprayed with rare earth (RE) solution was studied by means of pot experiments and field production experiments. The results showed that RE could increase the chlorophyll content and improve the ultrastructure of leaves and increase the number of grana and grana lamellae in the chloroplasts. So. it could increase the area of the photosynthetic membranes and the photosynthesis rate of the sugarcane. It could increase the activity of roots and promote the absorption of more N. P and K. and enhance nutrition metabolism. Sugarcane sprayed with RE solution had high levels of K. Ca. Zn. Cu and relatively low levels of Mn and Na. RE might regulate cane growth by regulating the balance of nutrient elements in the sugarcane.Tbe activity of acid and neutral invertases was raised in the stem elongation stage. But in the maturity stage, the activity of acid invertase was lowered while the activity of neutral invertase still remained very high. The sugarcane sprayed with RE solution grew quickly in the elongation stage and slowed down in the mature period to accumulate sucrose. RE could raise the drought resistance of sugarcane by maintaining the structure and function of the plasmolemma. controlling the osmotic pressure of cells and raising the plasticity of cell walls. It could also raise the salt tolerance of sugarcane by improving the permeability and the selective absorption of the plasmolemma. thus decreasing the harm due to high Na + content.