(1) Background: soil salinization has become a global problem that restricts agricultural production; thus, there is a need to explore the special survival strategies of halophytes in saline–alkali environments. (2) Methods: this study conducted a comparative analysis of the differences in metabolites and mineral elements between two indicator plants (Suaeda glauca and Suaeda salsa) in the study area. (3) Results: S. salsa leaves accumulated more total nitrogen (TN), total organic carbon (TOC), calcium (Ca), sodium (Na) and manganese (Mn). The Na/K analysis showed that S. salsa was more tolerant of saline–alkali environments than S. glauca. Metabolite analysis revealed a significant increase in added sugars in S. salsa compared with S. glauca and a significant accumulation of most organic acids associated with the TCA cycle, which suggests an enhancement in the flow of carbon from glycolysis to the TCA cycle. In addition, the content of phenolic substances, such as phenylpropane compounds and flavonols, also changed in saline–alkali environments, which may have promoted the metabolism of organic acids. (4) Conclusions: during the process of plant adaptation to salinity, the central metabolism of S. glauca was nitrogen metabolism, while that of S. salsa was organic acid metabolism.

With the continuous increase in saline–alkali land, sustainable development of the global environment and ecology have been seriously affected. This study compared the absorption and accumulation patterns of 11 elements in different parts (roots, stems and leaves) of different leaf Na regulation strategies of the pioneer plant Chenopodiaceae in saline–alkali land and evaluated the effects of soil nutrient status and soil salinity on the distribution of plant elements. The results showed that the changes in the content of Ca, Mg and Na in plants are affected by the salt-tolerant type and on different parts. Soil salinity had no significant effect on element concentrations in different parts of plants. The Pearson correlation coefficient showed that the correlation between plants and soil elements was different, and different parts of plants had the characteristics of selective absorption of soil elements. The salt tolerance type and soil mineral element concentrations explained most of the variation observed in element concentrations in Chenopodiaceae plants; the soil salinity property played only a minor role. It was concluded that the genetic factors are the prerequisite in the composition pattern of leaf elements in Chenopodiaceae, and soil factors are the key to determining element accumulation. These conclusions provide an effective reference for evaluating plant breeding and its response to environmental change in saline–alkali arid areas in Hulunbuir grassland and other parts of the world.