南沙群岛位于我国南海南部区域，其地理位置对我国海洋权益、发展战略和国家安全都十分重要。开展南沙群岛岛礁水深及地形监测与变化研究，对于系统了解南沙群岛、全面认知南海地形、保障南海军事安全、维护国家海洋权益都具有重要意义。本研究结合Sentinel-2和ICESat-2(ice, cloud, land elevation satellite-2)数据，采用主-被动融合测深算法，对南海南沙群岛的柏礁和北子岛等典型岛礁浅海区域的地形进行了反演研究及实验验证。研究结果如下：1)构建了基于多源卫星遥感反演南沙群岛典型岛礁浅海水深的高精度模型（R²>0.9，MAE(mean absolute error)<0.4m，RMSE(root mean squared error)<0.7m），经验证该模型具有较高的稳定性和可靠性。2)2016年至2024年间柏礁和北子岛地形及空间结构均发生了显著变化，柏礁因填海造陆工程，航道扩宽，陆地面积增加。北子岛沙滩与礁坪部分面积呈现此消彼长的关系，礁前斜坡区域则展现一定的年度波动。3)柏礁地形的显著变化与填海造陆工程的实施紧密相关，主要受人为因素影响。北子岛的变化则主要受自然因素影响，包括季风影响和台风活动，以及海水冲刷和沉积物再分布，这些自然过程与极端天气事件共同塑造了北子岛的地理形态。本研究对于基于多源卫星遥感手段u开展高效探测我国典型岛礁水深及地形具有重要借鉴意义，可为我国长期监测南沙群岛等区域浅海地形时空变化研究提供重要的技术支持。

The Nansha Islands are located in the southern part of the South China Sea. Its geographical location is very important to China's maritime rights, development strategy, and national security. It is of great significance to systematically understand the Nansha Islands, fully understand the topography of the South China Sea, ensure the military security of the South China Sea and safeguard the national maritime rights and interests to carry out the research on the monitoring and change of the water depth and topography of the Nansha Islands. In this study, combined with Sentinel-2 and ICESat-2 (ice, cloud, land elevation satellite-2)data, the active-passive fusion sounding algorithm is used to invert the topography of the shallow sea area of typical islands and reefs such as Bai Jiao and Beizi Dao in the Nansha Islands of the South China Sea. The findings are as follows: 1) A high-precision model for the shallow water depth of typical islands and reefs in the Nansha Islands based on multi-source satellite remote sensing inversion has been established (R2>0.9, MAE(mean absolute error)<0.4m, RMSE(root mean squared error)<0.7m), which is proven to have high stability and reliability. 2) From 2016 to 2024, significant topographic and spatial structural changes occurred on Bai Jiao and Beizi Dao, with Bai Jiao experiencing an expansion of the navigation channel and an increase in land area due to land reclamation projects. The beach area of Beizi Dao showed a relationship of this growth and reduction with the Bai Jiao flat area, while the reef front slope area exhibited certain annual fluctuations. 3) The significant changes in the topography of the Bai Jiao are closely related to the implementation of land reclamation projects, which are mainly affected by human factors. The change of Beizi Island is mainly affected by natural factors, including monsoon and typhoon activities, as well as seawater erosion and sediment redistribution. These natural processes and extreme weather events jointly shape the geographical morphology of Beizi Dao.This study has significant reference value for efficiently detecting the water depth and topography of typical islands and reefs in China using multi-source satellite remote sensing means and can provide important technical support for China's long-term monitoring of the topographic and temporal-spatial changes in shallow water areas such as the Nansha Islands.