Intensifying global warming has directed significant attention towards coastal tidal marshes for their efficient carbon sequestration capabilities. In recent years,tidal marshes in China have been facing the dual stresses of species invasion and reclamation disturbance,posing severe challenges to their carbon sink function. This study focused on the tidal marshes of the Yangtze Estuary. We assessed the dynamics in carbon density and the spatiotemporal heterogeneity of blue carbon stocks across different coastal sections and plant communities,employing field surveys,laboratory analyses,and remote sensing techniques. The results revealed that: (1) From 1990 to 2022,the area of tidal marshes in the Yangtze Estuary initially shrank and then expanded,with invasive Spartina alterniflora gradually replacing Phragmites australis as the dominant species,constituting 53.33% of the total tidal marsh area by 2022. (2) In coastal sections with long-term S. alterniflora invasion,both biomass carbon density and sediment carbon density were significantly higher than those of the native P. australis and Scirpus mariqueter communities. (3) In 2022,the total blue carbon stocks in the tidal marshes of the Yangtze Estuary reached (2794.84±691.04) Gg C,with S. alterniflora wetlands contributing over half (57%). Regionally,Chongming Island,Jiuduansha Shoal,and Nanhui Dongtan Shoal emerged as hotspots of blue carbon stocks within the Yangtze Estuary. (4) The expansion of S. alterniflora has become a key driver in the evolution of blue carbon pattern in the Yangtze Estuary over the past 33 years. Its carbon stocks increased from 27.88×10⁴ t in 2000 to 160×10⁴ t in 2022,while during the same period,the carbon stocks of P. australis and S. mariqueter decreased by 32% and 8%,respectively. This study enhances our understanding of blue carbon dynamics in the Yangtze Estuary tidal marshes and supports the assessment of estuarine carbon sink potential and invasive species management strategies.