Peppermint oil nanoemulsion was prepared by using the method of high pressure homogenizer with soybean protein and phosphatidylcholine as emulsifier. The microstructure， stability mechanism and antimicrobial property of peppermint oil nanoemulsion were studied. It was found that nanoemulsion droplet was in the spherical shape by using freezing cycle scanning electron microscopy to observe the microstructure of peppermint oil nanoemulsion， indicating that the soybean protein was completely adsorbed at the oil-water interface of the nanoemulsion and presented a core shell structure. The results of physical and chemical stability showed that the nanoemulsion of peppermint oil had higher pH value and salt ions resistance. The alkaline condition was more favorable for the maintenance of the physical and chemical stability of nanoemulsion. And the effect of CaCl2 concentration on it was greater than that of sodium chloride. After 30 days of storage in 4， 25 and 55 ℃， the size of emulsion increased by 30-50 nm and the retention rate of peppermint oil was higher than 85%. No obvious stratification occurred in the emulsion. It was found that that minimum bacteriostasis concentration of peppermint oil nanoemulsion to listeria monocytogenes and staphylococcus aureus were 0.5%， and the result was consistent with the bacteriostatic effect of the control group of peppermint oil. However， the results of the growth curve of the two microorganisms in 36 hours manifested that the nanoemulsion of peppermint oil had a longer time-effect depressant effect on microbial growth.