In 2019, soil and flue-cured tobacco leave samples were collected from 34 typical fields in 34 major tobacco-planting towns in 9 tobacco-planting counties in Yuxi City, soil rapidly available potassium (RAK) and available magnesium (AMg) and their interactions on the chemical and sensory qualities of tobacco leaves were determined and analyzed. The results showed that RAK and AMg ranged in 93.0-713.0 mg/kg and 40.0-610.0 mg/kg with a mean of 325.9 and 207.9 mg/kg, respectively. The percentages of fields deficient in RAK and AMg were 14.7% and 23.5%, respectively. With the increase of soil RAK, K of tobacco leaves increased and then decreased, while Mg of tobacco leaves increased, nicotine and total nitrogen of tobacco leaves decreased and then increased, and total sugar, reducing sugar, sugar-nicotine ratio and nitrogen-nicotine ratio of tobacco leaves are decreased, in which soil RAK and Mg of tobacco leaves showed a significant positive correlation (P<0.05). With the increase of soil AMg, K of tobacco leaves decreased, Mg of tobacco leaves increased, nicotine of tobacco leaves increased and then decreased, total nitrogen of tobacco leaves increased, total sugar, reducing sugar, sugar-nicotine ratio and nitrogen-nicotine ratio of tobacco leaves decreased and then increased, among which soil AMg was negatively and positively correlated with K and Mg of tobacco leaves, respectively (P<0.01). The increase in soil RAK and AMg significantly enhanced the style of clear sweet aroma and aroma content of tobacco leaves (P<0.05), respectively. Soil RAK-AMg interaction had a significant effect on total sugars, reducing sugars and nitrogen-nicotine ratio of tobacco leaves (P<0.05). Hence, to improve the quality of Yuxi tobacco leaves, additional K fertilizer should be applied on the basis of appropriate Mg fertilizer, and attention should also be paid to the effect of other fertilizers such as N fertilizer on K and Mg of tobacco leaves.