Objective To analyzed the clinical features,laboratory examination and sacroiliac joint CT signs of ankylosing spondylitis.Methods Of all 22 cases,20 were male,2 were female,the age ranges from 14 to 70 with average of 27.9.All patients accepted spiral CT axial scan of sacoiliac joint,their prominent clinical features and laboratory examination were registered.Results Hip pain,waist pain and lmitation of stoop were outstanding clinical features,their proportions were 63.3%,40.9%,31.8% respectively.Laboratory exanination:positive rates of HLA-B 27 and RF were respectively 100%,27.2%.Percentages of ESR speeding and CRP increasing were respectively 90.9%,31.8%.Among all CT signs,coarseness,dimness and erosion of SI joint had the highest percentage(68.1%).Others,such as osteosclerosis was in 50%,joint narrowing was in 36.3%,joint union was in 9.1%.Conclusion In patients with ankylosing spondyeitis, hip pain is common clinical feature.Positive HLA-B 27 ,mcreasing of ESR and CRP are valuable for diagnosis.SI joint CT examination often demonstrates joint coraseness,dimness and erosion.