Objective:To study the effect of synthetic antimicrobial peptides on Escherichia coli biofilm.Methods:The test tube method was used to establish the model of Escherichia coli biofilm.The samples were randomly divided into four groups:group A

by adding 4×MIC antimicrobial peptides to the samples

group B

by adding 1×MIC gentamicin to the samples

group C

by adding 4×MIC antimicrobial peptides and 1×MIC gentamicin to the samples

and group D

by adding phosphate buffered saline to the samples as a control.After 6 h the viable bacteria in the biofilm were counted following the method of colony count.The different changes in the biofilm were compared between the treated groups and the control group with scanning electron microscope.Results:The viable bacteria in group C were significantly decreased compared with the other three groups(P≤0.05).While compared with group D

the viable bacteria were decreased in group A and group B(P≤0.05).From the graph of scanning electron microscope the integrity of the Escherichia coli cell membrane was disrupted in group A and C.Conclusion:The results suggest that the killing effect of combination of antimicrobial peptides with gentamicin is significantly increased.