Abstract: Because of the essentiality of K and Mg fertilizer combination on banana's production, nutritional characteristics of Baxi banana (the most popular variety in China) and effects of K and Mg fertilizer combination on its growth were studied. Field trial results showed that nutrients mainly accumulated in pseudostems and leave of banana. The undulation of Mg/K ratio in leaves is biggest during the growth period of Baxi banana for the purpose of a high yield being 60 metric tones per hectare, the plants should absorb 275.3 kg N, 24.6 kg P, 900.0 kg K, 151.2 kg Ca, 73.2 kg Mg, 24.0 kg S, 2091.7 g Fe, 2910.6 g Mn, 228.6 g B and 435.6 g Zn, separately. Under the condition of Mg being rich in soils and Mg/K ratio being 6.87, the application of Mg combined with the application of a great deal of K didn' t have significant effect on the foliar nutrition, growth, agronomic characteristics, quality and yield of banana. We can draw the conclusion that Mg fertilizer may not need to be applied.