Both C-reactive protein and blood sedimentation can provide clues for the diagnosis of ankylosing spondylitis, but the diagnostic criteria for ankylosing spondylitis do not include C-reactive protein or blood sedimentation, so there is no such thing as which one of C-reactive protein and blood sedimentation is more accurate for diagnosing ankylosing spondylitis. The diagnostic criteria of ankylosing spondylitis mainly include clinical criteria and imaging criteria. Clinical criteria include limited lumbar spine movement, low back pain and morning stiffness, and low thoracic mobility, while imaging criteria are unilateral sacroiliac arthritis grade III-IV or bilateral sacroiliac joint grade II-IV. The diagnosis of ankylosing spondylitis can be confirmed by fulfilling the imaging criteria and more than one of the clinical criteria. C-reactive protein and blood sedimentation are mainly used as indicators of disease activity in the diagnosis of ankylosing spondylitis. Elevated C-reactive protein and blood sedimentation often indicate that the patient’s disease is in an active stage, but C-reactive protein and blood sedimentation do not provide a direct basis for the diagnosis of ankylosing spondylitis. It is recommended that patients with ankylosing spondylitis go to the Department of Rheumatology and Immunology of a regular hospital for a detailed consultation and follow the doctor’s instructions.