Soil salinization seriously inhibits crop growth and damages soil structure, which is the main abiotic stress affecting global agricultural sustainable development and soil ecological health. As the "second genome" of plants, the rhizosphere and endophytic microorganisms form a mutually beneficial symbiotic relationship with plants, which can promote plant growth and enhance their stress resistance, and has important development potential. Halophytes have long adapted to high salt environments, and their rhizosphere and endophytic microbiota have formed strong salt tolerance characteristics, making them a natural treasure trove for exploring salt tolerant and plant growth-promoting microbes. The mechanism by which these microorganisms enhance plant salt tolerance is analyzed from two aspects: their functional characteristics (e.g., production of plant growth hormones, ACC deaminase, and extracellular polysaccharides) and plant responses (e.g., osmotic regulation, antioxidant defense, and ion homeostasis). This article also explores the potential and preliminary effects of synthetic microbial communities in improving plant salt tolerance, and analyzes their advantages compared with single strains. Finally, focusing on current research issues and future directions, this review aims to provide theoretical references and practical ideas for the exploration and utilization of salt-tolerant plant growth-promoting microbes, the improvement of salt-tolerant crops, and the management of saline-alkali lands.