Considerable signal crosstalk exists in the regulatory network of senescence and stress response. Numerous senescence‐associated genes are also involved in plant stress tolerance. However, the underlying mechanisms and application potential of these genes in stress‐tolerant crop breeding remain poorly explored. We found that overexpression of SENESCENCE‐SUPPRESSED PROTEIN PHOSPHATASE (SSPP), a negative regulator of leaf senescence, significantly improved plant salt tolerance by increasing reactive oxygen species (ROS) scavenging in both Arabidopsis and soybean. However, overexpression of SSPP severely suppressed normal plant growth, limiting its direct use in agriculture. We previously revealed that the N‐terminal 1–14 residues of ACS7 (termed ‘N7’) negatively regulated its protein stability through the ubiquitin/proteasome pathway, and the N7‐mediated protein degradation was suppressed by environmental and senescence signals. To avoid the adverse effects of SSPP, the N7 element was fused to the N‐terminus of SSPP. We demonstrated that N7‐SSPP fusion gene effectively rescued SSPP‐induced growth suppression but maintained enhanced salt tolerance in Arabidopsis and soybean. Particularly, N7‐SSPP enhanced tolerance to long‐term salt stress and increased seed yield in soybean. These results suggest that N7‐SSPP overcomes the disadvantages of SSPP on plant growth inhibition and effectively improves salt tolerance through enhanced ROS scavenging, providing an effective strategy of using posttranslational regulatory element for salt‐tolerant crop breeding. Numerous senescence‐associated genes are also involved in stress tolerance, but the underlying mechanisms and application potentials are poorly investigated. We found that SSPP, a negative regulator of leaf senescence, enhances plant salt tolerance through ROS scavenging. Fusing N7, a regulatory element in the N‐degron pathway, to SSPP rescued SSPP‐induced growth suppression but did not affect salt tolerance in Arabidopsis and soybean. Notably, N7‐SSPP enhanced long‐term salt tolerance and increased yield in soybean. This study supported that manipulation of key senescence‐associated genes can effectively modulate plant stress responses and provided an effective strategy of using regulatory elements in the N‐degron pathway for salt‐tolerant crop breeding.