Accurately identifying and monitoring the changes in red mangrove pest and disease outbreaks is of great importance for the protection and restoration of red mangrove ecosystems. In 2023, a serious red mangrove pest and disease outbreak occurred in Tieshan Gang, Guangxi. Using the rapid data acquisition feature of the Huanjing Jianzai-2A/B(HJ-2A/B) satellite (HJ2A and HJ2B), the normalized difference vegetation index (NDVI) and fractional vegetation cover (FVC) parameters were inverted through remote sensing, and a threshold segmentation was performed to obtain the area and degree of damage to the red mangrove forests affected by the pest and disease. The results show that:① In 2023, the maximum area of red mangrove forests affected by pests and diseases in Tieshan Gang was 571.52 hm², accounting for 51.60% of the total area of red mangrove forests in Tieshan Gang.② When 0.1≤FVC≤0.5, the red mangrove forests are affected by pests and diseases. The degree of damage to the affected red mangrove forests was divided into three grades based on FVC, with 0.1≤FVC<0.23 being severe damage, 0.23≤FVC<0.46 being moderate damage, and 0.46≤FVC≤0.5 being light damage. Among them, the red mangrove forest with severe damage on October 8, 2023 was 257.82 hectares, accounting for 45.11% of the total affected red mangrove forest area at that time.③ On October 8, 2023, the area of red mangrove forests affected by pests and diseases in Tieshan Gang was the largest and the degree of damage was the most severe.