[Objective] This study aims to investigate the variation patterns of organic carbon storage in the plant-soil system following flooding restoration of degraded soda saline-alkali wetlands. [Methods] Typical long-term degraded marsh wetlands（alkali patches，Leymus chinensis grasslands）and Phragmites australis marshlands restored by flooding in the western Songnen Plain were selected as study sites. The aboveground and belowground vegetation biomass and physicochemical properties of the 1-meter soil profiles were measured to analyze the variation patterns of soil organic carbon（SOC）content and storage，along with their influencing factors，during the restoration of degraded saline-alkali wetlands. [Results] After restoration，the vegetation biomass and carbon pool of Phragmites australis marshlands reached 7 807.78 g/m² and 1.90 kg/m²，showing increases of 383.15% and 216.67%，respectively，compared with Leymus chinensis grasslands. The vegetation biomass and carbon pool of alkali patches were both zero. Flooding restoration promoted increases in both vegetation biomass and carbon storage. The SOC storage in the 1-meter soil profile of restored Phragmites australis marshlands reached 17.38 kg/m²，exceeding that of alkali patches and Leymus chinensis grasslands by 64.12% and 4.45%，respectively，with deeper layers exhibiting higher SOC than surface soils. Flooding restoration increased the SOC storage. SOC content and storage were significantly positively correlated with soil moisture（p<0.05），and negatively correlated with total nitrogen，total phosphorus，electrical conductivity，and the nitrogen-to-phosphorus ratio（p<0.05）. Significant differences in soil physicochemical properties were observed among alkali patches，Leymus chinensis grasslands， and Phragmites australis marshlands（p<0.05），and improvements in the soil environment during restoration facilitated SOC accumulation. [Conclusion] Flooding restoration of degraded soda saline-alkaline wetlands help enhance carbon sink capacity of the plant-soil system.