Objective To investigate the clinical value of MRI and X-ray in the early diagnosis of sacroiliac joint lesions in ankylosing spondylitis. Methods Selection in June 2015 to August 2016, our hospital diagnosed with ankylosing spondylitis patients with sacroiliac joint lesions in 92 cases as the research object, respectively for selected patients with MRI and X-ray imaging examination, compared to two kinds of checking methods for the detection of patients with lesions and the diagnosis of lesions in grading. Results The detection of MRI in the diagnosis of sacroiliac joint in ankylosing spondylitis rate was 100%, the X-ray detection rate was 80.43%, the detection rate of MRI was significantly higher than that of X-ray (P<0.05), compared with X-ray, MRI grade of sacroiliac joint in ankylosing spondylitis detection rate increased significantly, the 0 level of accurate diagnosis the rate was significantly higher than that of X-ray (P<0.05), other classification showed no significant difference (P>0.05). Compared with the X-ray and MRI imaging on invasion of ankylosing spondylitis sacroiliac joints, joint bone mass and cystic change of articular cartilage and joint swelling The detection rate of gap narrowing was significantly higher (P<0.05). Conclusion MRI in the diagnosis of ankylosing spondylitis sacroiliac joint lesions with a higher detection rate, but also can better show the lesions, with high clinical value.