Abstract: Soil salinization severely affect soil structure and fertility, exerting adverse effects on agricultural production and the sustainable development of the ecological environment. In this study, plant rhizosphere bacteria are screened out from saline-alkali soil in the central Gansu region, which could tolerate the highest concentration of 15% salt and pH was 11. It was assumed that the bacteria could regulate the soil environment and plant growth in the process of adapting to the saline-alkali environment. Therefore, a series of studies were conducted to investigate the physiological characteristics and growth-promoting properties of these bacteria. 16S rRNA sequence analysis identified the bacteria as Bacillus subtilis, named as L5, and its optimum growth conditions were as follows: 30 ℃ of the culture temperature, pH was 7, 2% of the NaCl concentration, 2% of theinoculum. Physiological characteristics research has found that L5 has the ability to decompose organic phosphorus and inorganic phosphorus, secrete indole acetic acid and produce iron carriers. Metabolomics analysis indicates that after L5 is subjected to saline-alkali stress, it adapts to and resists the stress environment by up-regulating the expression levels of amino acids and acidic metabolites, and these metabolites also have the function of promoting plant growth. Pot experiments confirmed that adding L5 bacterial solution reduced soil pH and electrical conductivity by 9.13% and 23.64%, increased soil activities of urease, alkaline phosphatase, sucrase, and organic matter content by 2.49, 2.96, 2.25 and 3.91 times, respectively. Available nitrogen, available phosphorus, and available potassium increased by 45.80%, 15.95%, and 46.80%, respectively. The chlorophyll content, proline content, catalase activity, peroxidase activity, and superoxide dismutase activity in wheat leaves increased by 3.30%, 52.96%, 55.89%, 61.11%, and 56.88%, respectively, while malondialdehyde content decreased by 30.83%. The study shows that L5 can significantly reduce the degree of soil salinity, improve soil fertility and promote plant growth, making it a valuable bacterial resource for improving saline-alkali soil environments.