Abstract: Sweet orange essential oil nanoemulsions and D-Limonene nanoemulsions were prepared by phase inversion composition method(PIC). The effects of antibacterial activities of sweet orange essential oil and D-limonene nanoemulsions against Escherichia coli,Bacillus subtilis,Staphylococcus aureus and Penicillium citrinum were studied using bacteriostatic circle method and the minimum inhibitory concentration method(MIC). The results showed that both sweet orange essential oil nanoemulsion and D-limonene nanoemulsion had great antibacterial effects. The antibacterial activity of D-limonene nanoemulsion was better than that of sweet orange essential oil nanoemulsions. The inhibitory zone diameters of 14% orange essential oil nanoemulsions against Escherichia coli,Bacillus subtilis,Staphylococcus aureus and Penicillium citrinum were 11.7,14.0,9.7 and 9.0 mm,while the inhibitory zone diameters of 14% D-limonene nanoemulsions against these microbes were 19.0,23.7,13.0 and 12.0 mm,respectively. Orange essential oil nanoemulsions had the strongest antibacterial activity on Bacillus subtilis with a MIC of 7.7%,and a weaker antibacterial activity on Staphylococcus aureus and Penicillium citrinum with a MIC of 11%. The MIC of sweet orange essential oil nanoemulsion against Escherichia coli was 7.7%~11%. The great antibacterial activities of sweet orange essential oil and D-limonene nanoemulsions were observed,and this result would provide a theoretical basis for the application of its antibacterial activity in food industry.