For a long time, soil salinization and the heavy metal contamination in coastal areas have been global environmental issues. The phytoremediation efficiency of heavy metals is relatively low due to the high salt content of the soil. This study investigated the effectiveness and mechanisms of co-remediation of cadmium (Cd) contaminated saline soils by Bacillus megaterium (Bm) and Suaeda salsa L. (S. salsa) using a pot experiment system, providing a novel approach for addressing complex pollution through combined remediation techniques. The results indicated that Bm significantly promotes plant growth and accelerates the translocation of Cd from soil to plants and from the roots to the aboveground parts of S. salsa. Bm significantly promoted plant growth by enhancing the absorption of Ca from the soil, reducing MDA (malondialdehyde) content in plants, and increased the POD (peroxidase) activity under all salt stress treatments and the SOD (superoxide dismutase) activity under 4.00% NaCl concentration treatment. Under a 4.00% NaCl concentration treatment, the bioconcentration factor (BCF) of Cd inoculated with Bm increased by 27.19%. These findings demonstrated that Bm enhanced the efficiency of Cd removal from saline soils by S. salsa, laying the foundation for further research into plant-microbe combined remediation techniques for Cd-contaminated saline soils.