Abstract: Objective To investigate the anti-phagocytosis effects of bacterial biofilm in invasive catheter.Methods From July 2010 through December 2011,32 samples of critical ventilator catheter specimens were collected from neonatal intensive care unit(NICU).The bacteria in inner membrane of the catheter were isolated and selected to simulate the biofilm in the catheter of the NICU under clinic usage.We observed the bio-membrane morphology and interactions between phagocytic cells and bacterial biofilm,and analyzed the relationship of catheter bio-membrane formation and catheter related infection.Results Totally 14 strains of Acinetobacter baumanii,a strains of Pseudomonas aerugionosa,6 strains of Staphylococcus,and 3 strains of fungus were isolated from the 32 samples.Eight strains of Acinetobacter baumanii could form bacterial biofilm.The bio-membrane was easily formed in invasive ductal by the adherence of bacteria,and scanning electron microscopy could be used for the observation of bacterial bio-membrane formation.The bio-membrane had anti-phagocytosis function.Conclusion The anti-phagocytosis effect of bacterial biofilm is an important factor for refractory infection.