Salt stress affects ion distribution in plant tissues. These salt-induced changes in ion distribution differ among plant varieties. In this study, we analyzed salt-tolerant inbred lines (8723 and 81162) and a salt-sensitive inbred line (P138) of maize under varying degrees of salt stress (0, 60, 140, 220 mmol/L NaCl) to explore the reasons for differences in salt resistance among the inbred lines. We measured the concentrations of Na⁺, K⁺, and Ca²⁺ in the testa, embryo, endosperm, root, stem, and leaf tissues, and determined the ratios of K⁺/Na⁺ and Ca²⁺/Na⁺ in germinating seeds and seedlings. In germinating seeds, the Na⁺ concentration was highest in the testa, followed by the embryo, and then the endosperm; the K⁺ concentration was highest in the embryo, followed by the testa, and then the endosperm. In seedlings, the highest level of Na⁺ was in the root, followed by the stem, and then the leaves; the highest levels of K⁺ were in the root and stem, followed by the leaves. With increasing NaCl concentrations in the salt treatment, the Na⁺ content increased gradually in germinating seeds and seedlings of the three maize lines. In germinating seeds, the range of the increase in Na⁺ content was smaller in the salt-tolerant lines 8723 and 81162 than in the salt-sensitive line P138, and the salt-tolerant lines accumulated less Na⁺ than did the salt-sensitive line. In seedlings, the range of the increase in Na⁺ content was larger in the salt-tolerant lines 8723 and 81162 than in the salt-sensitive line P138, and the salt-tolerant lines accumulated higher levels of Na⁺ in the roots and lower levels of Na⁺ in the stem and leaves. As the NaCl concentration in the salt treatment increased, the K⁺ and Ca²⁺ contents decreased gradually in germinating seeds and seedlings of the three maize lines. In germinating seeds and in seedlings, the salt-tolerant lines 8723 and 81162 showed smaller ranges of decreased K⁺ contents and contained higher concentrations of K⁺ compared with the salt-sensitive line P138. In seedlings, the salt-tolerant lines 8723 and 81162 showed smaller ranges of decreased Ca²⁺ contents compared with the salt-sensitive line P138. However, in germinating seeds, there was no significant difference in the range of decreased Ca²⁺ content among the three maize lines. With increasing NaCl concentrations in the salt treatment, the ratios of K⁺/Na⁺ and Ca²⁺/Na⁺ decreased in germinating seeds and seedlings. The K⁺/Na⁺ ratio was higher in the salt-tolerant lines 8723 and 81162 than in the salt-sensitive line P138. Germinating seeds and seedlings of the salt-tolerant lines 81162 and 8723 retained higher K⁺/Na⁺ ratios by adjusting ion homeostasis to improve salt resistance.