As a major invasive plant in China's coastal areas， Spartina alterniflora has a serious negative impact on the ecological balance of coastal ecosystems， especially posing a great threat to the ecological security of the Tianjin-Hebei coastal area. Based on six periods of Landsat TM/OLI and Sentinel-2 images from 2000 to 2022， four methods， including expansion intensity， centroid， standard deviation ellipse， and fractal dimension， were used to reveal the spatiotemporal characteristics of Spartina alterniflora in the Tianjin-Hebei coastal area and analyze its driving factors. The results showed that the area of Spartina alterniflora in the coastal area of Tianjin-Hebei increased from 10.08 hm² in 2000 to 425.62 hm² in 2022， an increase of 41.22 times， and the overall expansion rate showed a trend of first increasing and then decreasing and then increasing. From 2000 to 2015， Tianjin Binhai New District was in a period of rapid expansion， with an expansion rate of 27.28 hm²/a， and the growth rate of Spartina alterniflora in Huanghua was slow. From 2015 to 2022， Huanghua expanded the fastest， at 16.13 hm²/a， and Tangshan first appeared in 2015 and continued to expand rapidly， with an expansion rate of 5.25 hm²/a. The distribution of Spartina alterniflora in the Tianjin-Hebei coastal area is skewed along the northeast-southwest axis， and the centroid moved southward by 19.09 km from 2000 to 2022. The growth rate of Spartina alterniflora in the southern part was faster than that in the northern part. The spatial structure of Spartina alterniflora is becoming more complex， and the spatial complexity of Spartina alterniflora in Huanghua， Cangzhou， Hebei is higher than that in Binhai New District， Tianjin. In addition， the changes and spatiotemporal differentiation characteristics of Spartina alterniflora are influenced by different policy regulations. The research results provide a basis for the control and management of Spartina alterniflora in the Tianjin-Hebei coastal area and are of great significance for the management.