This research initially concentrated fermentation broth by forward osmosis (FO) process, and investigated the effects of membrane orientation, type and concentration of draw solution, as well as crossflow velocity on the concentration performance. The results showed that under FO mode, the optimal concentration performance was achieved with 4.0 mol/L MgCl2?6H2O and a flow rate of 1200 mL/min.Under this condition, the caproic acid concentration was increased from 10.2 g/L to 22.9 g/L, and the total acid recovery and caproic acid recovery were 54.8% and 62.9%, respectively. Subsequent secondary concentration was conducted via rotary evaporation under reduced pressure, where the influence of temperature on concentration efficiency was explored. 65℃ was identified as the optimal operating temperature, elevating the caproic acid concentration to 40.6 g/L after this step. Finally, the pH of the secondary concentrated solution was adjusted to investigate its impact on acidification-induced oil separation. The results showed that when the pH was adjusted to 3.5, caproic acid was successfully precipitated as an oil phase, achieving a final concentration of 476.4 g/L and a purity of 68.0%, which realized a substantial improvement in both concentration and purity of caproic acid. It is verified that the coupled process of forward osmosis-vacuum rotary evaporation-acidification oil extraction can effectively enhance the separation and purification of caproic acid, providing a new strategy for the separation and extraction of caproic acid from fermentation broth. However, the purity of caproic acid obtained by this process is still insufficient for the application of fine chemicals. Further research will consider adopting rectification and other methods to further improve the purity of caproic acid.