Objective To investigate the diagnostic value of human leukocyte antigen (HLA )-B27 for ankylosing spondylitis (AS) .Methods 2 768 patients with suspected AS were enrolled ,including 600 patients with confirmed AS .Flow cytometry was performed to detect blood HLA-B27 .Results Among 2 768 patients with suspected AS ,598(21 .6% ) patients were found HLA-B27 positive and 2 170(78 .4% ) patients negative .Difference of HLA-B27 positive rates between male and female patients was sta-tistically significant(P< 0 .05) .HLA-B27 positive rate of patients aged 20 - < 40 years was significantly higher than the others (P<0 .05) .Among 600 patients with confirmed AS ,536 cases(89 .3% ) was found HLA-B27 positive .Conclusion HLA-B27 de-tection combined with clinical manifestations contribute to early diagnosis of AS .