The aim of this study was to investigate possible association of a single nucleotide polymorphism (SNP) at position 9250 in exon 7 of the Osteopontin gehe (OPN gene 9250) with ankylosing spondylitis (AS). A case control association study was performed in 120 AS patients and 106 matched controls, consented to participate in the study. OPN gene 9250 polymorphism was detected by polymerase chain reaction (PCR) and direct sequencing. The frequency of the TC+CC genotype of the OPN gene 9250 was significantly higher (25.83% vs 12.26%, p < 0.05) and the frequency of C allele was significantly higher (17.50% vs 8.96%, p < 0.01) in AS patients than in controls. There were significant differences in OPN gene 9250 allele and phenotype frequencies between the AS patients and controls (p < 0.05). OPN gene 9250 polymorphism appears to be associated with susceptibility to AS in Chinese patients.