Abstract: To explore the bactericidal effect, cell structure and biofilm removal mechanism of ozone water combined with Lactobacillus paracasei Z21 fermented supernatant on E. coli O157:H7 in mung bean sprouts, this experiment combined treatment of artificially contaminated E. coli O157:H7 to select the optimal bactericidal conditions. The bactericidal mechanism of ozone water combined with Z21 supernatant was studied by flow cytometry, scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR) and raman spectroscopy. The effect of ozone water combined with Z21 fermented supernatant on E. coli O157:H7 biofilm was studied by colony counting and extracellular polymer analysis. The results showed that 1.5 mg/L ozone water combined with 10% (V/V) Z21 fermented supernatant had the best bactericidal effect on E. coli O157:H7, and the total number of bacteria decreased by 2.81 lg CFU/g. Compared with the control group, the combined treatment destroyed polysaccharides, lipid and protein structures in the cell walls and membranes of E. coli O157:H7, increased the permeability of cell membrane, and changed the morphology. The combined treatment presented a strong removal effect on biofilm, and the extracellular polymer content of the biofilm was significantly reduced (P<0.05). This study could provide a theoretical basis for the removal of Escherichia coli biofilm and preservation of agricultural products.