Abstract: Fifteen hybrids were obtained by crossing 5 different genotypes of flue-cured tobacco with different potassium content selected according to the Griffing Ⅱ model. Genetic effects of 4 main physiological characteristics of root were analyzed at the fast-growing stage of flue-cured tobacco under plenty of potash via pot cultivating method. According to the results, there were significant differences between general combining ability and special combining ability of the 4 traits. Their broad-sense heritability was over 60%, indicating that variance in these traits was mainly controlled by genetic factors. The heritability of root volume and CEC of flue-cured tobacco was mainly controlled by additive effects, suggesting that in breeding tobacco cultivars for high-volume and high-CEC, selection at early generations is more efficient. The heritability of root vigor and ATPase activity of flue-cured tobacco was mainly controlled by dominance effects, and the heterosis of F1 generation was also stronger. High-vigor and high-activity of ATPase could be obtained by heterosis utilization. Nongda203×NC628 and Yunyan85×NC628 could be chosen as materials to breed for nutrient efficient flue-cured tobacco varieties (lines) for their good comprehensive performance.