Abstract: The research aimed to study the characteristic of ionic homeostasis of annual seedlings of Populus ×euramericanna under irrigation with non-magnetized and magnetized 0 or 4.0 g·L^-1 NaCl solution for 30 days in the growing season. The ion contents of K⁺, Na⁺, Ca²⁺ and Mg²⁺ in the lea-ves and roots were measured by atomic absorption spectrophotometry (AAS). The ion homeostasis coefficient (K) and the ion selective transport coefficient (S_Xi,Na) from root system to leaves were analyzed. Compared with the unsalted treatment, the ion contents of Na⁺ and Ca²⁺, S_K,Na and S_Mg,Na increased in leaves and roots under NaCl stress, while the K⁺ and Mg²⁺ ion content, the ratio of K⁺/Na⁺ and S_Ca,Na decreased. Compared with the non-magnetized NaCl solution (NM), the magnetized NaCl solution (M) made leaves and roots maintain lower content of Na⁺ but higher content of K⁺ and the K⁺/Na⁺. Compared with the NM, the content of Ca²⁺ decreased while that of Mg²⁺ increased in the M. In M, K was higher than that in NM, and there was significant increase in the leaves than that in the roots. The ratios of S_K,Na and S_Mg,Na in leaves and roots in M were higher than those in NM, while the ratio of S_Ca,Na was lower. The magnetized NaCl solution decreased Na⁺ content, increased K⁺, Ca²⁺ and Mg²⁺ content, and maintained higher K⁺/Na⁺, which was beneficial for the physiological metabolism of the whole plant. So, the magnetic effect could promote the re-establishment of ionic homeostasis by ions selective absorption and transportation under NaCl stress.