Abstract: Blue carbon refers to the carbon stored in mangrove, salt marsh and seagrass bed ecosystems occupying about 55% carbon stocks of all coastal wetlands. We analyzed mangrove changes in Beihai, Guangxi during 1988－2018 based on 5-year-period remote sensing images for mangrove blue carbon stock estimation. The mangrove area in Beihai increased from 459 ha to 3320 ha during 1988－2018, with an annual growth rate of 6.8%. Deforestation and pond digging had the greatest impact on some mangroves (dredging activities) with 150 ha loss between 1998 and 2003. The paper calculated the total carbon of mangroves in Beihai over the past 30 years based on IPCC guidelines for national greenhouse gas inventories. The carbon stock increased steadily from 32064 t in 1988 to 214830 t in 2018, with an annual growth rate of 6.5%. Excavation activities contributed much to carbon stocks decrease as the removal of soil carbon, with the largest loss of 80783 t between 1998 and 2003. The paper suggested that the local management should combine all stakeholders to strengthen mangrove conservation and restoration formulating more scientific, reasonable, efficient and practical policies and measures so as to better serve the national strategy of carbon neutral and peak carbon dioxide.