Floating/emergent aquatic vegetation (FEAV) is an important group of aquatic vegetation in lakes, and its area or coverage is a significant parameter for assessing lake ecological health and estimating carbon sequestration potential. Accurately and extensively obtaining information on the area/coverage and changes of FEAV in lakes is crucial for lake ecological restoration and carbon sink accounting. Satellite remote sensing is the most effective means to obtain the area or coverage of FEAV in lakes. However, traditional satellite monitoring methods can only determine the presence or absence of aquatic vegetation within satellite pixels, and cannot quantitatively estimate the coverage of aquatic vegetation in the pixels. Consequently, it is impossible to obtain precise quantitative data on the area/coverage of FEAV in lakes. To address this issue, we utilized UAV, Sentinel-2 MSI, and Landsat 8 OLI data, employing the XGBoost model and a stepwise upscaling approach to develop quantitative estimation models for FEAV coverage at pixel scales based on Sentinel-2 MSI and Landsat 8 OLI, successfully applying these models to the four major freshwater lakes. The models were successfully applied to Chinas four largest freshwater lakes. The results showed that the test sets of the two estimation models based on Sentinel and Landsat images hadR2 of 0.95 and 0.97, root mean square error of 7.85% and 4.80%, and mean absolute error of 5.35% and 3.35%, respectively. From 1990 to 2022, FEAV area in Lake Poyang and Lake Dongting showed highly significant increasing trends, while Lake Taihu showed an increasing and then decreasing trend, while Lake Hongze had a non-significant increasing trend. The estimation models constructed using Sentinel and Landsat images have achieved quantification and long-term monitoring of coverage in the four major freshwater lakes, demonstrating good robustness and application potential. These are expected to provide methodological and data support for carbon sink calculations and carbon sequestration potential assessments in lake ecosystems.