Abstract: Objective: To analyze the correlation of the bone mineral density(BMD) changes of lumbar and femoral neck with age,gender,disease duration,hip lesion and acute phase reactant in patients with ankylosing spondylitis(AS).Methods: The BMD of lumbar(L₂-L₄) and femoral neck were detected using Dual-energy X-ray absorptiometry method,and T value was used as the diagnosis criteria of osteoporosis.Results: The BMD of lumbar and femoral neck in male AS patient was significantly lower than that in female AS patient(P<0.05).The difference of the BMD of femoral neck between the patients with AS complicated with and without hip lesion was not statistically significant(P>0.05).The T value of BMD of lumbar was negatively correlated with the age of patient(P<0.05),but the disease duration and acute phase reactant were not correlated with the BMD of AS patient(P>0.05).Conclusions: Compared with female AS patient,the osteopenia and osteoporosis in male AS patient are ease to happen,and the occurrence rate of osteoporosis of lumbar increases with the age of patient increasing.Disease duration,hip lesion and acute phase reactant have no significant influence on the BMD change in AS patient.