With the depletion of fossil fuels, there is an urgent need to find renewable alternative chemicals to alleviate the world energy crisis. The production technology of medium chain fatty acids (MCFAs) based on chain elongation (CE) process seems to be sustainable. Based on the detailed summary and analysis of the CE metabolic pathways, substrate types, CE microorganisms, fermentation process and fermentation products, this paper also comprehensively revealed the main rate-limiting steps in the production process of MCFAs and provided suggestions for future research. In addition, the combination of electrochemical technology and traditional fermentation was expected to significantly increase the production of MCFAs, thus becoming a potential new technology for organic waste recycling.