Objective To explore MRI of sacroiliac joint.Methods MRI was applied to 33 patients on transaxial FSE T2WI and SE T1 WI,coronal FSE T2 WI and two coronal FSPGR.Results Sacroiliac joints of 7 patients were normal,and all the sequences could directly show the cartilage of normal sacroiliac joints.The other 26 patients suffered from ankylosing spondylitis(AS),and cartilage abnormality appeared in 42 sacroiliac joints from 52 joints.The irregular thickened or tortuous ones replaced the linear intermediate signals on T1WI and T2WI.Conclusion Such measures do good to MRI of normal sacroiliac joint structure and pathological changes as optimization of scanning parameters,selection of proper scanning method and coil,as well as application of T2WI and FSPGR in phase fat suppression technology.