Soda saline-alkaline land is the predominant type of saline-alkaline soil in the western Songnen Plain of China, which severely restricts local crop growth and agricultural development. Given the varying tolerance levels among different crops, unraveling their adaptation mechanisms has become a fundamental approach for identifying key genes, breeding new saline-alkaline tolerant crop varieties, and enhancing the productivity of saline-alkaline lands. To investigate the tolerance levels, adaptive mechanisms, and rhizosphere microbial community differences of various Poaceae and Fabaceae crops in soda saline-alkaline soil, this study focused on widely cultivated species from the Songnen Plain. The selected crops included Poaceae species (corn, sorghum, oat) and Fabaceae (soybean, alfalfa, and sesbania). The research examined the effects of varying degrees of saline-alkaline stress on their growth and physiological characteristics. Furthermore, principal component analysis and membership function methodology were employed to comprehensively evaluate their saline-alkaline tolerance. The results indicated that as the intensity of saline?alkaline stress increased, the above-ground and below-ground growth of all crops was significantly inhibited. However, the growth phenotype of sorghum did not change significantly when the saline?alkaline level increased from S2 to S3. Corn and soybean were most severely affected by Na+ damage; in the S3 treatment, their leaf Na+ concentrations were 33.7 times and 21.5 times higher than those in the S1 treatment, respectively. Among the Poaceae crops, sorghum leaves maintained a higher K+/Na+ ratio under saline?alkaline stress (7.42 under the S3 treatment, higher than other crops). Under the S3 treatment, soluble sugar content increased by 44.9% compared to the S1 treatment, and proline content was 8.0 times that of the S1 treatment, thereby enhancing their osmotic adjustment capacity. Concurrently, the activity of superoxide dismutase in the cells increased significantly, effectively mitigating oxidative damage. Among the Fabaceae crops, Compared with S1, the K+ content in sesbania leaves increased significantly by 31.9% under the S3 treatment, thereby maintaining intracellular ion homeostasis. Simultaneously, soluble protein content and peroxidase activity increased by 18.4% and 32.1%, respectively, effectively mitigating the damage caused by reactive oxygen species to the crop. Based on the comprehensive evaluation, sorghum and sesbania demonstrated stronger saline-alkaline tolerance among the selected Poaceae and Fabaceae crops, respectively. Furthermore, under saline-alkaline stress conditions, the rhizosphere soil of sorghum showed significant enrichment of nine bacterial genera, including Pseudomonas, while that of sesbania exhibited enrichment of fourteen genera, such as Pontibacter. These microbial genera show significant potential for enhancing crop tolerance to saline-alkaline conditions. The results of this study provide a theoretical basis for screening saline-alkaline tolerant germplasm and breeding new crop varieties, while laying the groundwork for improving agricultural productivity in saline-alkaline soils and elucidating the mechanisms underlying crop tolerance to such stress.