Objective:To assess antimicrobial activity of Fe 3O 4 nanozymes against Candida albicans. Methods:Fe 3O 4 nanozymes were prepared by using a modified hydrothermal synthesis method. Candida albicans suspensions were divided into 4 groups: nanozyme group treated with 0.5 g/L Fe 3O 4 nanozymes, H 2O 2 group treated with 0.1% H 2O 2, combination group treated with 0.5 g/L Fe 3O 4 nanozymes and 0.1% H 2O 2, and control group receiving no treatment. Candida albicans in the above 4 groups was all cultured with Sabouraud liquid medium, the absorbance value at 600 nm was detected every 2 hours, and the growth of Candida albicans was observed. After 2-hour treatment, the morphology of Candida albicans in the 4 groups was observed by scanning electron microscopy; after plate coating, Candida albicans was cultured at 36 ℃ for 48 hours, colonies were observed and counted, and the inhibition rate of colony formation was calculated. One-way analysis of variance was used for comparing means among several groups, and least significant difference (LSD) - t test for multiple comparisons. Results:A relatively stable survival curve of Candida albicans was observed in the control group, while the growth of Candida albicans was inhibited in the nanozyme group, H 2O 2 group and combination group. The colony count significantly differed among the control group, H 2O 2 group, nanozyme group and combination group (124 830 ± 45 170, 86 330 ± 13 960, 91 670 ± 31 370 and 30 330 ± 3010 respectively; F = 9.41, P < 0.05) , and was significantly lower in the combination group than in the control group ( t = 4.63, P < 0.05) . There was a significant difference in the colony-formation inhibition rate among the H 2O 2 group, nanozyme group and combination group (30.84% ± 5.00%, 26.57% ± 11.24%, 75.70% ± 2.42% respectively; F = 9.413, P < 0.01) , and the combination group showed a significantly higher inhibition rate compared with the H 2O 2 group and nanozyme group ( t = 8.08, 4.27 respectively, both P < 0.01) . Scanning electron microscopy showed changes in the morphology of Candida albicans treated with H 2O 2 and nanozymes alone or in combination, including shrinkage, rupture and even collapse. Conclusion:Fe 3O 4 nanozymes combined with H 2O 2 have obvious antimicrobial effect against Candida albicans.