Electro-fermentation (EF) has been proposed as a method to improve the yield of medium-chain fatty acid (MCFA). In this study, MCFA production from Chinese liquor wastewater (yellow water) was investigated and corresponding composite electron donors (lactate and ethanol in yellow water) were investigated by different electrical stimulation modes. The caproate yield under whole period electrical stimulation increased by 250.9% compared with open circuit. The oxidation-dominated and reduction-dominated periods of the fermentation process were divided, and the segmented electrical stimulation experiment showed the caproate yield under reduction-dominated EF system further increased by 288.5% compared with open circuit. The microbial diversity analysis demonstrated that Clostridium 12 might be enriched better by keeping open circuit during EDs consumption, meanwhile the bacteria with potential negative effects on CE were inhibited. The electrical stimulation mode of EF process was optimized and provided a new way to recycle organic wastewater.