Rubisco activase (RCA) is the key regulatory enzyme in photosynthetic carbon assimilation that governs the activation state of Rubisco, which is the rate-limiting enzyme in CO 2 fixation. In general, salinity seriously inhibits photosynthesis and yield in glycophytic crops, it paradoxically enhances photosynthetic efficiency in halophytes, such as Suaeda salsa ( S. salsa). However, the potential mechanism still remains unknown. Here, we cloned and characterized the Rubisco activase gene ( SsRCA, 1425 bp) from the euhalophyte S. salsa, which encodes a 475-amino-acid protein. The SsRCA gene expression level and the RCA protein content were increased by 246% and 20%, respectively, under NaCl condition in S. salsa. To investigate the function of SsRCA, we generated SsRCA-overexpressing Arabidopsis thaliana lines. Compared with the wild type (WT), the RCA activity in transgenic lines exhibited 64% higher, and the net photosynthetic rate (Pn) were elevated by 41%, at the 100 mM NaCl stress conditions. Meanwhile, under NaCl stress, the transgenic plants showed lower Na + and MDA content, enhanced K + and proline accumulation, and reduced oxidative damage compared to WT. These results demonstrated that SsRCA overexpression enhanced the salt tolerance of plants by optimizing Rubisco activation efficiency. Our findings will provide a novel halophyte-derived genetic resource for engineering crops with improved photosynthetic resilience in saline environments.