To investigate the spatial and temporal evolution of salt marsh vegetation in Jiangsu Yancheng Wetland Rare Bird National Nature Reserve, a phenological feature composite method was used to invert the area of four types of salt marsh vegetation ( Spartina alterniflora , Phragmites australis, Suaeda salsa and Imperata cylindrica) in the core area of the Reserve from 1984-2021, and to analyze its spatial and temporal evolution and driving mechanism. The results showed that the total area of salt marsh vegetation in the core area increased from 11 113.2.hm²to 16 528.14.hm², with a compound annual growth rate of 1.11%, mainly due to the ability of Spartina alterniflora to preserve the beach and promote siltation. Spartina alterniflora and Phragmites australis, by occupying a large number of Suaeda salsa beach, Phragmites australis beach and light beach, the area increased by 4 968.62.hm2 and 8 806.95.hm², with compound annual growth rates of 26.67% and 6.88%, respectively. The areas of Suaeda salsa and Imperata cylindrica decreased by 3 494.25.hm² and 4 867.38.hm² respectively by the superimposed effects of natural factors such as ecological niche competition and artificial disturbances such as aquaculture bases, with a compound annual growth rate of -3.14% and -8.11%, resulting in the severe fragmentation of the suitable habitats.