The cultivation of Saccharina japonica (formerly Laminaria japonica) has been a cornerstone in China’s marine aquaculture industry for nearly seven decades, contributing significantly to food security, economic development, and environmental sustainability. This article examines the historical development, technological innovations, and challenges facing the S. japonica cultivation industry, with a focus on sustainability in the context of climate change. The key achievements, such as the summer seedling method, floating raft cultivation systems, and the development of high-yield cultivars, have enabled large-scale production, with yields increasing from 22 t (dry weight) in 1952 to 170,000 t in 2021. However, the kelp industry was affected by ocean warming, acidification, and other marine influences. These changes threaten kelp growth and natural seaweed-derived ecosystems and their stability. Offshore cultivation and mechanization are emerging as potential solutions to these challenges, though both are in their infancy. The article also explores the role of S. japonica cultivation in carbon sequestration and its potential for mitigation during climate change, while acknowledging the limitations of current practices. Overall, the sustainability of the S. japonica industry will depend on continuous technical innovation, its adaptation to environmental changes, and the development of advanced technologies and strains for the offshore and mechanized cultivation.