The mangrove ecosystem is regarded as a crucial coastal “blue carbon” ecosystem and the characteristics of carbon sources and sinks and their budget are currently a hot topic of research in China on “carbon peaking and carbon neutrality.” Through the collection and compilation of relevant domestic and international research and data, this study summarizes the characteristics of carbon sources and sinks, methodologies for carbon accounting, and budgets of carbon sources and sinks in Chinese mangrove ecosystems. Carbon sources and sinks in mangrove ecosystems primarily include vegetation and soil carbon stocks and greenhouse gases. In Chinese mangrove ecosystems, the annual carbon sequestration of vegetation ranges from 4.0×10⁴ to 6.1×10⁴ t C/a, whereas the annual carbon sequestration of soil ranges from 4.4×10⁴ to 9.7×10⁴ t C/a. The total CH₄ emissions are approximately 1.0×10³ t C/a and the ecosystem-scale carbon sequestration ranges from 0.7×10⁵ to 1.5×10⁵ t C/a. Over a 100-year period, CH₄ emissions can offset approximately 5% of the net ecosystem productivity in terms of carbon sequestration effects. The net lateral carbon output is 0.5×10⁵ to 1.5×10⁵ t C/a. Furthermore, the contribution of mangrove carbon sinks to total ecosystem carbon sequestration in China and their challenges have been discussed thoroughly. Future efforts should focus on strengthening mangrove conservation and restoration, actively monitoring carbon sequestration, and ensuring a balance between the carbon sequestration function and other vital ecological services.