The interaction between plant communities is an important source of biodiversity in coastal wetlands and the foundation for maintaining the diversity of coastal wetland ecosystems. Suaeda salsa is an indigenous species in Yancheng coastal wetland, which is of great significance in the maintenance of ecological functions. This paper took the core area of Yancheng National Nature Reserve as the research case, took the 12 remote sensing images from 1983 to 2021 as the data source, and introduced the Coulomb's law to analyze the spatiotemporal change characteristics of Phragmites australis community and Spartina alterniflora community extrusion on Suaeda salsa community. The results showed that: (1) The area of Phragmites australis and Spartina alterniflora communities increased linearly with time, and the area of Suaeda salsa communities increased first and then decreased. (2) The extrusion force of Phragmites australis community on Suaeda salsa community ($\overrightarrow{F_{l j}}$) increased linearly and was divided into three stages with 1992 and 2002 as nodes. The track of the action point was mainly eastward, moving about 4700 m. The extrusion force of Spartina alterniflora community on Suaeda salsa community ($\overrightarrow{F_{m j}}$) increased at first and then decreased, which also showed the characteristics of three stages. The track point moved about 700 m to the west and 270 m to the north. The combined extrusion force of Phragmites australis community and Spartina alterniflora community on Suaeda salsa community (F_合) showed a linear increase. The force direction was on the left side of NNE direction before 2002, and on the right side of NE direction after 2002. The track point moved to the northeast, mainly to the east. (3) RDA ranking can reflect the relationship among Suaeda salsa community area and $\overrightarrow{F_{l j}}$, $\overrightarrow{F_{m j}}$ and F_合. The area variable of Suaeda salsa in 12 periods was distributed in four quadrants clockwise according to "three- two-one-four" by F_合 and distributed in four quadrants in the order of "three-four-one-two" by $\overrightarrow{F_{l j}}$, and $\overrightarrow{F_{m j}}$, with obvious stage characteristics. (4) The results of multiple regression showed that the influence of $\overrightarrow{F_{l j}}$ on Suaeda salsa was larger than that of $\overrightarrow{F_{m j}}$. There was the high correlation among landscape pattern indexes (ED, LSI, SHDI and AI) and $\overrightarrow{F_{l j}}$, $\overrightarrow{F_{m j}}$ and F_合. Research on the interaction relationship of plant communities in Yancheng coastal wetland can provide theoretical reference for the ecological restoration of coastal wetland and the sustainable construction of the world natural heritage site.