Abstract: The growth range, interannual biomass and biological carbon storage of Sonneratia apetala on Qi'ao Island from 1999 to 2019 was quantitatively calculated on the basis of multi-period remote sensing images and field-measured sample data to research the effect of fast carbon fixation of Sonneratia apetala and the reasons for the changes were analyzed. The biomass inversion model of the study area was obtained: B=75.906-6.144×SR-10.728×Variance, where P < 0.01, R²=0.700. As the results show, the area of Sonneratia apetala in 1999, 2003, 2009, 2013 and 2019 were 0, 29.520, 114.245, 140.280 and 332.399 hm² respectively; the carbon stocks in 1999, 2003, 2009, 2013 and 2019 were 0, 4 872.74, 15 051.14, 25 892.55, 55 969.24 t respectively; the carbon sequestration rates from 1999 to 2003, 2003 to 2009, 2009 to 2013 and 2013 to 2019 are 3.66, 7.55, 19.48, 28.06 t/(hm²·a) respectively; and the carbon density per unit area of Sonneratia apetala has increased by 168.38 t/hm² in the past 20 years. Compared with other mangrove species and subtropical broad-leaved forests at the same latitude, Sonneratia apetala is an ideal mangrove plant with faster carbon sequestration rate and greater carbon storage and can be used to restore bare land coasts.