Estuarine wetlands are critical global carbon sinks, significantly influencing the climate through carbon cycling. The invasive plant Spartina alterniflora has earned attention for its effects on these processes in wetland ecosystems. This study examines the impact of S. alterniflora on soil carbon dynamics in the Minjiang River estuarine wetland, Fujian Province, by comparing soil organic carbon (SOC) components in particulate organic matter (POM) and mineral-associated organic matter (MAOM) between S. alterniflora and native Cyperus malaccensis stands. We also investigated soil carbon dioxide (CO2) emissions and organic carbon mineralization to assess how plant invasion alters carbon cycling in wetland soils. The invasion of S. alterniflora increased dissolved organic carbon (DOC), microbial biomass carbon (MBC), and labile organic carbon (LOC) in MAOM while reducing these carbon components in POM. LOC and MBC contents in MAOM were 15 % and 32 % higher, respectively, in S. alterniflora wetlands compared to C. malaccensis wetlands. This suggests that S. alterniflora shifts the composition and stability of SOC, making MAOM a more significant carbon pool. The invasion also led to higher CO2 emissions and greater temperature sensitivity. Additionally, S. alterniflora soils exhibited a negative priming effect upon glucose addition, likely due to the strong association between active organic carbon and minerals in MAOM, which protects organic matter from decomposition. These results highlight the intricate impacts of plant invasion on soil carbon cycling and offer insights for predicting carbon dynamics in estuarine wetlands.