To investigate the roles of CD147 in the pathogenesis and development of ankylosing spondylitis (AS). Flow cytometry was used to detect the expression levels of CD147 in peripheral monocytes and T lymphocytes of 30 AS patients, 30 rheumatoid arthritis (RA) patients and 30 healthy controls (HC). reverse transcription-polymerase chain reaction (RT-PCR) was used to evaluate the expression levels of CD147 mRNA in peripheral blood mononuclear cells (PBMC). Then the expression levels of CD147 were compared among the groups. And a correlation analysis was conducted between CD147 levels and disease activity indices of AS patients. The mean fluorescence intensities of CD147 in monocytes of AS, RA and HC group were 213.5 ± 37.8, 228.7 ± 49.7 and 163.6 ± 44.8, and in T lymphocytes 36.8 ± 10.1, 40.2 ± 10.5 and 28.3 ± 10.6 respectively. Both the expression levels of CD147 in monocytes and T lymphocytes of AS patients were slightly lower than those of RA patients. But the differences was not statistically significant (P > 0.05). Both the CD147 levels in monocytes and T lymphocytes of AS and RA group were significantly higher than those of HC group (P < 0.05). The expression levels of CD147 mRNA in PBMC of AS and RA group were significantly higher than those of HC group (P < 0.05) while no significant difference was found between AS and RA group (P > 0.05). Both the expression levels of CD147 in monocytes and T lymphocytes of AS patients were positively correlated with the patients' erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). The expressions of CD147 in peripheral monocytes and T lymphocytes of AS patients are up-regulated and their levels are positively correlated with patients' ESR and CRP. It implies that CD147 plays critical roles in the pathogenesis and development of AS.