Objective To understand the formation of bacterial biofilm in polyvinyl chloride(PVC) hoses pipeline at the connection end of hemodialysis device and water supply loop, and control bacterial biofilm in water treatment system. Methods The hoses were divided into two groups(group A and B) according to their service life and material, group A was transparent hoses used for 7 years and group B was red opaque hoses used for 5 years, specimens of group A and B were conducted different experimental treatment (group A₁ and B₁ didn't undergo any treatment; group A₂ and B₂ immersed in hydrogen peroxide disinfectant for 20 minutes; group A₃ and B₃:the inner wall of hoses were stirred with sterile cotton swabs and immersed in hydrogen peroxide disinfectant for 20 minutes), bacterial biofilm was observed under electron microscope. Results Group A₁ showed formation of overlapped and reticulated biofilm; group A₂ and A₃ showed that there were fissure and crack in bacterial biofilm, which could not completely fall off. In group B₁, the planar bulges were bacterial biofilm; group B₂ showed scattered globules; group B₃ showed the presence of free rod-like bacteria. Group A hoses (without any experimental treatment) were scanned by electron microscope at different multiples, showing that they were mainly composed of clustered bacteria. Conclusion The removal efficiency of bacterial biofilm is closely related to the complexity and overlapping degree of its morphology and structure. The study on hose material, time point of bacterial biofilm formation and disinfection treatment method for the connection of hemodialysis device and water supply loop can better carry out the control strategy research of bacterial biofilm in water treatment system.