Coastal slope is a fundamental land characteristic that can influence the hydrodynamic and morphological processes, which is the essential parameter to calculate the wave setup and wave runup for further estimating extreme coastal water levels. Slope information of coastal zones also plays a key role in estimating the coastline erosion and evaluating the coastal vulnerability under sea level rise. However, accurate estimates of coastal slopes are currently limited, especially over sparsely populated and remote areas. The recent ICESat-2 photon-counting lidar provides unprecedented along-track dense and accurate height measurements in coastal zones. This study aims to demonstrate the potential of ICESat-2 measurements to estimate coastal slope of sandy beach at a large scale, and the proposed method is tested in Texas, USA. The validation with local airborne lidar data (with an average slope of 0.023 in Texas) indicates that, the ICESat-2 derived coastal slopes (0.026) have much better accuracy than current large-scale coastal slopes (0.0032) derived from SRTM and MERIT DEMs. With globally covered ICESat-2 datasets, this method can be expanded to estimate coastal slopes even at a global scale.