Abstract: Coastal salt marshes, as an important coastal ecosystem, provides significant ecological service functions in coastal protection, biodiversity maintenance, carbon sequestration and pollution reduction. Timely and accurate monitoring of the distribution and dynamic changes of coastal salt marshes is of great significance for the scientific management and protection of the local coastal salt marsh ecosystem. This study used multisource domestic high spatial resolution satellite imagery in 2019 and 2021, combined with the UAV’s advantages of strong autonomy, flexibility, and no cloud occlusion affect, to monitor the distribution of coastal salt marshes in Guangxi. In 2021, the distribution areas of coastal salt marshes in Guangxi were 1 341.40 hm². Salt marshes distributed in 3 coastal cities of Guangxi. And the areas of salt marshes in Beihai, Fangchenggang, and Qinzhou were 1 247.82 hm², 49.73 hm² and 43.85 hm², accounting for 93.02%, 3.71% and 3.27% of the total salt marsh area in Guangxi, respectively. Compared with that in 2019, the salt marsh area in Guangxi decreased by 108.96 hm² in 2021. Specifically, the area of Spartina alterniflora decreased by 107.05 hm² in Beihai city, and the area of other salt marsh type (Cyperus malaccensis and Phragmites australis) decreased by 1.91 hm² in Qinzhou City, whereas the area of salt marshes in Fangchenggang City remained unchanged. The control of invasive species S. alterniflora in Guangxi has been effective, the area of S. alterniflora decreased dramatically. However as the S. alterniflora area still increased in some local areas in Guangxi, it is still necessary to strengthen the monitoring and control of S. alterniflora.