Abstract: With prolonged stress time under different sea-salt concentrations, Na⁺, K⁺, Ca²⁺, Mg²⁺ distribution and transportation in roots, stems and leaves of Sumu No.2 Napier grass seedlings were analyzed and compared with those of N51(CK). Na⁺ content increased but K⁺, Ca²⁺, Mg²⁺ content and the ratios of K⁺/Na⁺ decreased in all organs of Sumu No.2 and N51 as the sea-salt concentration increasd. With increasing time under 10 g/L sea-salt concentration stress, the Na⁺ content in roots of Sumu No.2 was higher than those of N51. Under 4-10 g/L sea-salt concentration stress, the Na⁺ content in stems of Sumu No.2 was significantly lower than that of N51, and that in leaves of Sumu No.2 was lower than in N51; the K⁺ content in roots and stems of Sumu No.2 was significantly higher than those of N51, while the K⁺ content in leaves of Sumu No.2 and N51 were not the same; The ratios of K⁺/Na⁺ in leaves of Sumu No.2 were higher than in N51; The transport selectivity of S_K⁺/Na⁺ (stem/root)of Sumu No.2 was 1.02-2.19 times that of N51, except that Sumu No.2 was lower than that of N51 after 7 d stress with 4 g/L sea-salt concentration. It appears that a major characteristic of the salt tolerance mechanism in Sumu No.2 seedlings is a high transport selectivity of S_K⁺/Na⁺ (stem/root)that can intercept more Na⁺ in roots and selectively transport more K⁺ from root to stem resulting in a higher K⁺/Na⁺ ratios in stems and leaves under sea-salt stress.