AIM: To study the polymorphism of flagellin A genotype and its significance in Helicobacter pyiori ( H. Pylori).METHODS: As the template, genome DNA was purified from six clinical isolates of H. Pylori from outpatients, and the corresponding flagellin A fragments were amplified by polymerase chain reaction. All these products were sequenced. These sequences were compared with each other, and analyzed by software of FASTA program.RESULTS: Specific PCR products were amplified from all of these H. Pylori isolates and no length divergence was found among them. Compared with each other, the highest ungapped identity is 99. 10%, while the lowest is 94.65%.Using FASTA program, the alignments between query and library sequences derived from different H. Pylori strains were higher than 90%.CONCLUSION: The nucleotide sequence of flagellin A in H.pylori is highly conservative with incident divergence. This information may be useful for gene diagnosis and further study on flagellar antigen phenotype.