Since the industrial revolution, the concentration of greenhouse gases in the atmosphere has risen rapidly due to human activities, which has seriously affected the global climate. The development of blue carbon industry has become an essential measure for people to cope with climate change. Cultivated seaweeds carbon sinks are an important component of blue carbon. Based on the data of seaweeds cultivation in eight coastal provinces of China, this research calculates the total economic value of the carbon sink of the cultivated seaweeds, and analyzes its spatiotemporal differentiation characteristics. The LMDI index decomposition method was used to analyze the influencing factors of the total economic value of carbon sink of cultivated seaweeds in China, which provided a reference for the reasonable calculation and evaluation of the economic value of carbon sink of cultivated seaweeds. The results showed that the carbon sink and total economic value of cultivated seaweeds in China showed an overall upward trend from 2009 to 2021,which reached 0.87 million tons and 48.8 billion CNY in 2021, respectively. The carbon sink of different seaweeds from high to low were Saccharina japonica, Gracilaria spp., Porphyra sensu lato, Undaria pinnatifida, and others (Sargassum fusiforme, Eucheuma muricatum, Gelidium amansii, and Ulva prolifera). The carbon removal capacities per unit area from high to low were S. japonica, G. spp., U. pinnatifida, others (S. fusiforme, E. muricatum, G. amansii, and U. prolifera) and Porphyra sensu lato. The total economic value of cultivated seaweeds carbon sinks in Fujian, Shandong, and Liaoning provinces were relatively high, while in other provinces those were relatively low. The culture efficiency effect (EFE) and culture area effect (AE) had a strong driving effect on the total economic value of carbon sinks in cultivated seaweeds. Research had found that the carbon sink potential of cultivated seaweeds in China must be addressed and could create huge economic benefits. The total economic value of cultivated seaweeds could be improved by adjusting the cultivation species and structure reasonably. Suggestions were proposed from the government, the scientific research unites, the industry practitioners and the public. Efforts should be made to enhance the function and value of fishery carbon sink, especially the cultivated seaweeds industries, to promote the high quality development of the fishery industry that contribute to mitigating global climate change, and realize the grand goal of " carbon-peaking and carbon neutrality".