The application discloses a kind of composite plantessential oil, nano emulsion and its preparation method and application.The composite plantessential oil is composed of moslaessential oil, peppermint essential oil, clove essential oil and pepper essential oil with volume ratio (1.8-2.2) :(0.8-1.2) :(0.8-1.2) :(0.8-1.2).The nano emulsion contains the above-mentioned composite plant essential oil with concentration 8-12%, and is prepared by high-energy emulsification method.Through nano carrier technology and essential oil synergistic effect, the nano emulsion has strong antioxidant and broad-spectrum antibacterial dual excellent activity, and highlights the superiority of compounding, and has wide application prospect in food preservation.