Aqueous enzymatic method is a green oil extraction technology with limited industrial application owing to the need for demulsification of the oil body intermediate product. Existing demulsification methods have problems including low demulsification rates and high costs, such that new methods are needed. Free fatty acids produced by lipid hydrolysis can affect the stability of peanut oil body (POB) at a certain concentration. After screening even-carbon fatty acids with carbon chain lengths below ten, caproic acid was selected for demulsification of POB using response surface methodology and a Box–Behnken design. Under the optimal conditions (caproic acid concentration, 0.22%; material-to-liquid ratio, 1:4.7 (w/v); time, 61 min; and temperature, 79 C), a demulsification rate of 97.87% was achieved. Caproic acid not only adjusted the reaction system pH to cause aggregation of the POB interfacial proteins, but also decreased the interfacial tension and viscoelasticity of the interfacial film with increasing caproic acid concentration to realize POB demulsification. Compared with pressed oil and soxhlet-extracted oil, the acid value and peroxide value of caproic acid demulsified oil were increased, while the unsaturated fatty acid content and oxidation induction time were decreased. However, the tocopherol and tocotrienol contents were higher than those of the soxhlet-extracted oil. This study provides a new method for the demulsification of POB.