Abstract: Objective:To investigate the relationship between tumor necrosis factor α（TNF-α） gene polymorphism of the promoter region 308 site and ankylosing spondylitis（AS）.Methods:Genomic DNA from 112 AS patients and 96 healthy controls,98 HLA-B27 positive AS patients and 14 HLA-B27 negative AS patients were genotyped for TNF-α gene 308 site polymorphism by polymerase chain reaction——restriction fragment length polymorphisms（PCR-RFLP）.Results:Three genotypes（GG、GA and AA） frequencies in AS patients were 60.71%,36.61% and 2.68%,and in controls were 81.25%,17.71% and 1.04%,respectively.The allele frequencies（G and A） in AS patients were 0.790 and 0.210,and in controls were 0.901 and 0.099,respectively.Allele A frequency in AS patients was significantly increased compared with the controls.Significant difference was also found in the distribution of genotypes between HLA-B27 positive AS patients and HLA-B27 negative AS patients.Conclusion:The gene polymorphism of the promoter region 308 sit of TNF-α is associated with AS,and allele A may play a role in AS susceptibility.