Objective To explore the application value of X-ray, CT and MRI in early ankylosing spondylitis sacroiliac joint lesions in the diagnosis. Methods 100 cases of patients with early sacroiliac joint in ankylosing spondylitis in our hospital from September 2013 to September 2014 were selected, and were given X-ray,CT and MRI examination.The imaging manifestations and classification of the three methods of inspection were observed and compared. Results MRI diagnosis of articular surface erosion and joint bone mass with cystic change detection rate was significantly higher than the CT and X-ray diagnosis, the difference was statistically significant, (all P<0.05); and MRI diagnosis of articular cartilage swelling detection rate was significantly higher than the X-ray, with no significant difference (P>0.05). The detection rate in the 0 stage ankylosing spondylitis, MRI was significantly higher than that of CT and X-ray diagnosis, the difference was statistically significant, (all P<0.05); detection rate of CT and MRI examination of grade I, grade II ankylosing spondylitis were significantly higher than that of X-ray diagnosis, the difference was statistically significant (all P<0.05). Conclusion X-ray, CT and MRI all have certain application value in the early sacroiliac joint in ankylosing spondylitis diagnosis, of which MRI of soft tissue lesions and grading of ankylosing spondylitis higher detection rate.