Abstract: Fishery carbon sink, as an important type of marine carbon sink, plays an indispensable role in mitigating global climate change. Kelp (Saccharina japonica), a typical carbon sink organism, absorbs and sequesters substantial amounts of CO₂ through photosynthesis. China is the world’s largest producer of farmed kelp, which exhibits significant carbon sequestration potential. However, existing assessments of its carbon sink capacity remain incomplete. Based on data from the China Fishery Statistical Yearbook (2004−2023), this study estimated the carbon sink amount from kelp aquaculture in China over the past two decades, including kelp biomass carbon, deposited carbon, transported carbon, and refractory dissolved organic carbon (RDOC). Using the autoregressive integrated moving average (ARIMA) model, this study predicted the kelp aquaculture carbon sink potential in China from 2024 to 2033. The results show that the kelp aquaculture carbon sink amount in China increased from 1.4462−1.4937 million tonnes in 2004 to 2.6898−2.7485 million tonnes in 2023, representing an increase of 85.0%. Based on the ARIMA model, carbon sink amount from kelp aquaculture in China will continue to grow over the next decade, reaching an estimated 3.6172−3.6746 million tonnes by 2033, which is 2.5 times the level in 2004.