Abstract: Pot experiment of potassium redistribution at different parts of tobacco mesophyll cells was carried out in greenhouse. The result showed that the potassium content of mesophyll increased with potassium supplied under normal or drought conditions. Most of the potassium was in the vacuole, little in the chloroplast and least in the mitochondrion. There were obvious redistribution of potassium among vacuole, mitochondrion, chloroplast under drought. The potassium content in vacuole of tobacco changed little without potassium supply, but its ratio reduced. Both of potassium content and ratio of chloroplast and mitochondrion were increased obviously. The potassium content in vacuole of tobacco increased, but the ratio reduced with potassium supplied under drought. Mitochondrion potassium content and ratio were also reduced, and potassium content and proportion were increased in chloroplast with supplied potassium. The result also showed that reduction of photosynthesis activity of mesophyll cells could be prevented by supplied potassium. 