Mangrove forests are intertidal herbaceous and woody wetland communities that grow on tropical and subtropical coastal mudflats and riverbanks, and are one of the most productive and biologically significant ecosystems, providing important support for the development of coastal ecology, economy and society in all aspects. However, mangrove forests are one of the most vulnerable and threatened ecosystems in the world due to their special growing locations. Aquaculture, urban development, environmental pollution, deforestation, and sea-level rise are constant threats to mangrove growth. This loss of mangrove forests greatly threatens the survival and development of human beings. In recent years, the management and conservation of mangrove forests have received worldwide attention, including methods for the scientific and effective monitoring of mangrove forests. Understanding of the spatial and temporal changes and trends of mangrove forests is very important for the conservation, restoration and sustainable management of mangrove forests. Based on the Google Earth Engine (GEE) cloud computing platform, this study used global mangrove distribution data and Landsat series optical image feature index data, combined with Theil-Sen median trend analysis, Mann-Kendall test, and Hurst index to analyze the spatio-temporal distribution characteristics of global mangrove forests, their spatio-temporal evolution trends and their sustainability characteristics. Firstly, the global mangrove area declined and then increased from 1990 to 2020, with a net decrease of 52174.18km² in total area, and overall disappeared at an average rate of 1.2% per year. The most serious region of mangrove loss was in Southeast Asia over the world, followed by Australia and New Zealand, South America, and East and Southern Africa. The area of mangrove forests showing changes in degradation trends (82.8%) was significantly larger than the area of improved areas (17.43%), with the most pronounced degradation trends in Australia and New Zealand. Then, the global trend of mangrove forest change in 2015-2020 improved, 73.85% of the global mangrove forests are sustainable in the future, with the area of persistently improving areas (38.58%) being larger than the area of persistently degrading areas (33.06%), and the sustainability of the improving areas being significantly higher than that of the unsustainable ones, indicating an overall improving trend change in global mangrove forests after 2020. The spatio-temporal changes and trends of global mangrove forests can provide important supports for biodiversity conservation, coastal economic development, and sustainable improvement of ecological environment, and will have a significant impact on the assessment of the realization of the United Nations 2030 Sustainable Development Goals (SDGs).