The studies on the effects of potassium nutrient in different stages of growth on leaf yield and quality of flue-cured tobacco were conducted by way of sand culture. The results demonstrated that tobacco leaf yields was significantly correlated with K application in early and mid stages, while K content in leaf was highly significantly correlated with K application in later stage of growth. The results of path analyses showed that K application in mid stage had strong effect on the leaf yield and leaf K content, K application in early stage had some effect on leaf K level and less effect on the leaf yield. K application in later growth stage growth is very important to increase the leaf K content, and split application of K fertilizer was also suggested.