Abstract: Objective: to investigate the bactericidal activities of recombinant fusion protein of human β-defensin 3（hBD3） and bactericidal/permeability increasing protein（BPI） against Gram-negative bacteria.Methods: rhBD3-BPI was serially diluted and incubated with standard Pseudomonas aeruginosa or clinically-isolated gram-negative bacteria strain.Minimal inhibitory concentration（MIC） and minimal bactericidal concentration（MBC） were determined.Recombinant hBD3 served as control.Results: rhBD3-BPI had a MIC against the bacteria at 1-4 μg·mL^-1,and a MBC at 4-8 μg·mL^-1.As a control,rhBD3 had a MIC at 4-8 μg·mL^-1 and a MBC at 8-16 μg·mL^-1.Significantly statistical difference in the MIC and MBC of rhBD3-BPI and rhBD3 was found against each individual gram-negative bacterial strain.Conclusion: rhBD3-BPI has bactericidal activities against gram-negative strains.