The Chinese government has made tremendous efforts to promote the advancement of the aquaculture industry through the technical resources of its extension system. However, research on the Chinese aquaculture extension system is limited. The purpose of this study is to provide an overview of the role of China’s aquaculture extension system in the sustainable development of aquaculture since the Reform and Opening Up in 1978. We find that China has established a relatively comprehensive aquaculture extension system under the leadership of the Ministry of Agriculture and Rural Affairs. The five-level state-owned extension organizations are the main body, and research institutions, universities, social organizations, and aquatic enterprises are important segments. Technical extension programs, demonstration zones, and technical consultation are the three popular aquaculture extension models. However, problems such as insufficient funding, outmoded staff structures, and inefficient management systems should be addressed to promote the prosperity of the aquaculture industry.