[Objective]To explore the reason of ulnar impaction syndrome misdiagnosed by tissue injury in wrist.[Method]From December 1998 to December 2005,216 cases who were diagnosed for soft tissue injury in ulnar wrist were checked and discriminated according to X-ray and MRI of the injured wrist,and 48 cases were re-diagnosed for ulnar impaction syndrome.The misdiagnosis rate was 22.2%.[Result]Most cases of ulnar impaction syndrome had positive lunar variance(68.8%).Carpal avascular necrosis were found in about 27.1% of cases through X-ray of wrist and 100% through MRI.Different degree changes of abnormal signal intensity were found in soft tissue,triangular fibro cartilage(TFC) and carpal bones by MRI which displayed swelling of soft tissue in carpal joint,strip-shape high signal intensity or mixed signal intensity at ligament around wrist and enhanced signal intensity at TFC area extending to ulnar carpal articular facet.The appearance of MRI in carpal bones showed local abnormal signal,articular cartilage thickening and hydropsia in bone below cartilage and marrow.[Conclusion]The misdiagnosis can be reduced through elevating acquaintance level of ulnar impaction syndrome basing on clinical symptoms,making the most use of imaging,especially MRI.