Abstract: The improvement and utilization of saline-alkali land are crucial for expanding reserved arable land resources and ensuring food security in China. As the “second genome” of plants, rhizosphere microbiomes have great potential in enhancing crop tolerance to saline-alkali stress and promoting crop adaptation to specific soil environments. Among these microorganisms, arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) are beneficial microbes that can substantially increase plant salt tolerance. In this paper, we summarize the progress on the separate roles of AMF or PGPR in enhancing plant resistance to saline conditions. Then the synergistic mechanisms by which the two microbial groups enhance plant salt tolerance, including the improvement of nutrient efficiency, regulation of hormonal homeostasis, promotion of induced systemic resistance, and modulation of transcription factor expression are elucidated. Finally, we propose future amelioration directions based on the cross-kingdom interactions between AMF and PGPR. The aim is to comprehensively understand the mechanisms underlying salinity tolerance and plant growth promoting effects of microbiomes under saline conditions. It also provides essential scientific support for exploiting microbial resources and developing biotechnological strategies for amelioration of saline-alkali lands.