In order to study the distribution of Mg content in flue-cured tobacco leaves in Yuxi City, Yunnan, we collected tobacco leaves and soil samples, and clarified the overall distribution of Mg content in flue-cured tobacco leaves, its distribution at different altitudes and slopes and its relationship with soil total N, total P, rapidly available K, available Mg, available B and Cl^- by means of descriptive statistics, ANOVA, correlation analysis and regression analysis. The results showed that the average Mg content of flue-cured tobacco leaves was 4.28 g/kg with a variation of 0.94~9.17 g/kg and 41.2% of leaves was in the suitable range (4.0~15 g/kg) of Mg. Except for the 1 700-1 900 m altitude zone where the mean Mg content of leaves (4.67 g/kg and 5.57 g/kg) was in the suitable range, mild Mg deficiency (2.0~4.0 g/kg) was found in the <1 700 m, 1 900-2 000 m and >2 000 m altitude zones. Mg content of leaves was in the appropriate range in the <5° and >10° slope zones (4.55 g/kg and 4.34 g/kg) while deficient in the 5°-10° slope zone. Mg content of leaves showed a significant linear correlation with the contents of total soil phosphorus and effective Mg(P<0.01), and a significant linear correlation with the contents of soil rapidly available K, available B and Cl^-(P<0.05). In Yuxi tobacco region, appropriate applications of P, K, Mg and B fertilizers are needed to further regulate the application of N and Cl fertilizers.