The Yangtze River Delta (hereinafter referred to as the YRD), as one of the regions rich in forest resources in China, possesses immense carbon sequestration potential. Accurately capturing and assessing forest disturbances in the YRD is of great significance for enhancing forest management and ecological environmental protection in the region. This study employed the LandTrendr change detection algorithm and the method of Landsat 5-8 time-series stacking based on the Google Earth Engine (GEE) cloud platform to monitor forest disturbances and gains in the YRD over a span of 30 years from 1991 to 2020. The results indicated that the overall accuracy of the LandTrendr algorithm in monitoring forest disturbances and gains reached 88.5%, with both the producer's accuracy and user's accuracy exceeding 80%, demonstrating effective monitoring of forest disturbances and gains in the YRD. The total area of forest disturbances in the YRD was 9646.96 km2, while the total area of forest gains was 37205.46 km2. Over the past 30 years, the total forest area in the YRD has shown an increasing trend. The LandTrendr algorithm, based on the GEE cloud platform, has achieved precise monitoring of forest disturbances and gains in the YRD.