Seagrass meadows are virtual blue carbon ecosystems facing a dramatic decline on a global scale. Tracking the status and trends of seagrass meadows, which is still pending on large scales, is an emerging priority for their conservation and restoration. Here, we develop a semi-automatic procedure to identify and map seagrass meadows. Using Sentinel-2 data in Google Earth Engine (GEE) platform, a map is generated, showing a total of 11113.4 ha of seagrass meadows in coastal China in 2020. There exists the largest extent (6450.3 ha) in the coast of the South China Sea, while the second area (3909.5 ha) is in the Yellow Sea-Bohai Sea, and the seagrass meadows in the East China Sea cover about 753.6 ha. Our results provide the baseline data of seagrass meadows distribution in coastal China, and this study can be of reference for mapping seagrass meadows on a broader or even global scale.