Abstract: Coastlines serve as one of the most essential basic geographic elements. However，conventional methods generally face challenges in the accurate detection of their location，due to instantaneous remote sensing imaging and dynamic tidal phenomena. In response to this，this study developed a novel coastline extraction model that incorporates information on surface moisture content derived from long-time-series satellite remote sensing imagery. First，all available remote sensing images covering the study area during the target period were acquired to construct a high-quality remote sensing image stack. Second，the wetness components indicative of the surface moisture content were obtained using the tasseled cap transformation （TCT），from which a wetness index stack was constructed. Then，the wetness components were subjected to maximum value synthesis using the maximum spectral index composite （MSIC） algorithm，generating a maximum water surface composite image. Finally，the composite image was segmented using the OTSU algorithm to extract accurate coastline information. Validation experiments were conducted on Zhoushan Island using the Google Earth Engine （GEE） cloud computing platform and remote sensing imagery from the operational land imager （OLI） onboard the Landsat 8 satellite. The results indicate that the proposed model can precisely locate different types of coastlines with high spatial accuracy. Compared to visual interpretation，the model exhibited a mean deviation and a root mean square error （RMSE） of 3.42 m and 6.79 m，respectively，with 99.42% of validation points falling within one pixel width. This study provides an effective technical framework for high-accuracy coastline extraction，holding great significance for scientific management and sustainable development of coastal resources.