The objective of this study was to detect the expression frequency of HLA-DR15 in patients with aplastic anemia (AA) and myelodysplastic syndrome (MDS), to investigate the relation of expression frequency with diseases and to analyze the relationship between immunoglobulin, T lymphocyte subsets and HLA-DR15. HLA-DR15 expression was detected by PCR-SSP; immunoglobulin was detected by immune turbidimetry; T cell subsets were detected by flow cytometry. The results showed that the expression rates of HLA-DR15 in AA and MDS as well as normal control groups were 78.6%, 63.2% and 24.6% respectively. The difference between AA, MDS and the normal control groups was statistically significant (p < 0.01). OR (odds ratios) values of AA and MDS groups were 11.262, 4.710 respectively. Compared with normal control group, expression rate of HLA-DR15 in hematologic malignancy group was not significantly different. The immunoglobulin level and abnormal T cell subsets in AA and MDS groups were statistically different between HLA-DR15 positive and negative groups (p > 0.05). It is concluded that the frequency of HLA-DR15 antigen in AA and MDS patients is significantly higher than that in normal control and hematologic malignancy group. OR value>1 showed a positive correlation between the diseases and HLA-DR15. HLA-DR15 is a susceptible gene in AA and MDS. The abnormalities of immunoglobulin level and ratios of T cell subsets in AA and MDS are common, but are not associated significantly with the expression of HLA-DR15.