Objective   To set up a more effective fluorescein labeling method to trace lipopolysaccharide (LPS).    Methods   LPS was disaggregated into monomers and then a surface activator was added

followed by labeled with fluorescein isothiocyanate (FITC) in the neutral solution at 37℃ for 18 h. The FITC-LPS was further purified by using a Ultra-4 millipore filter. By examination of spectrophotometer

a comparative analysis of labeling efficiency was performed between the purified solution and the raw solution. The tracing efficiency of our FITC-labeled LPS was compared with that of the 2 commercial products by laser confocal electron microscopy.    Results   The end product of FITC-LPS was detected effectively under  confocal microscope

expressing fine tagging ability. This new method had a labeling rate of FITC to LPS ratio (33.13∶1) than the traditional method does.    Conclusion   The new method combining the surface activator and ultra-filter shows a higher FITC-LPS labeling efficiency

and can be used to trace LPS in experimental research.