Abstract: 【Objective】 To study the response of cigar tobacco root morphology and potassium metabolism characteristics to ridge height and potassium application mode, which could provide theoretical basis for improving the root growth environment of cigar tobacco and enhancing the quality of cigar leaf. 【Method】 Using the cigar tobacco variety Chuanxue No. 1 as the test material, a 2-factor, 3-level split-area test of ridge height and split-application of potassium was designed, with 3 ridge height levels（35 cm for high ridges, 30 cm for medium ridges, and 25 cm for low ridges） as the main zone and 3 modes of potassium application（1 time of potassium application, 2 times of potassium application, and3 times of potassium application） as the subzones, to analyze the root morphology, potassium content, potassium accumulation intensity and the expression of key genes of potassium metabolism in the tobacco plants in the different treatments.【Result】Root morphology indexes of cigar tobacco showed an overall trend of gradual increase during the growth process. Under the same ridge height, the root morphology indexes were higher in the treatments of 1 and 2 times of potassium application than in the treatment of 3 times of potassium application at 40-50 d after transplanting, and the highest indexes were found in the treatment of 3 times of potassium application at 50 d after transplanting. Under the same potassium application mode, the root morphology indexes were higher in the high and medium ridge height treatments than in the low ridge height treatment. As the growth period progressed, root potassium content showed an overall trend of increasing and then decreasing, stem and leaf potassium content gradually decreased, and the potassium accumulation intensity of root, stem, leaf and the whole plant increased first and then decreased. Under the same ridge height, the potassium content of each organ was higher after 50 d of transplanting in 2 or 3 times of potassium application; the potassium accumulation intensity of each organ was higher in 3 times of potassium application. Under the same potassium application mode, the potassium content of all organs was higher in the high and medium ridge height treatments at 50 d after transplanting, and the potassium accumulation intensity of root, stem, leaf and whole plant was higher in the high and medium ridge height treatments. The relative expression of inward-flowing potassium ion channel genes BNKT1 and NtKC1, potassium transporter protein genes NtTPK1 and NtHAK1 were up-regulated by in 2 and 3 times of potassium application in high ridges, the relative expression of outward-flowing potassium ion channel gene NTORK1 was low, and the relative expression of potassium transporter protein gene NtKT12 was up-regulated by 3 times of potassium applications in high ridges.【Conclusion】 The combination of high and medium ridges（ridge heights 35 and 30 cm） with 3 doses of potassium application（60% potassium base + 20% at 30 d after planting + 20% at 45 d after planting） is favorable to promote the root system development of cigar tobacco and enhance the capacity of potassium accumulation in tobacco plants.