Abstract： Objective To explore the clinical,pathological and imaging features of Ewing's sarcoma in pelvis and to improve knowledge and diagnosis of the disease.Methods A retrospective analysis of the clinical,pathological and imaging data of pathologically confirmed 13 cases of Ewing's sarcoma in pelvis was carried out between May 2008 and March 2016 in the Affiliated Hospital of Hangzhou Normal University,the Third Hospital of Hebei Medical University and the Second Hospital of Hebei Medical University.Results The median age 13 cases of pelvic primary Ewing's sarcoma was 17 years old.The X-ray and CT imagings showed osteolytic and mixed bone destruction,CT showed mixed type in 10 cases,8 cases of bone tumors as a flocculent,10 cases of bone expansion failure,10 cases of periosteal reaction,the layered 5 cases,radial in 5 cases.Thirteen cases showed soft tissue mass,soft tissue mass was equal or slightly lower density.Four cases showed heterogeneous contrast enhancement.The lesions showed low signal in T1 WI and mixed high signal in T2WI of magnetic resonance imaging(MRI).The boundary of the lesions were obscure,and 5 cases had patchy necrosis area,and 9 cases had incomplete false capsule,surrounding soft tissue was violated.Four cases showed heterogeneous contrast enhancement after MRI enhancement scan.Conclusions The age of onset of Ewing's sarcoma of the pelvis is more concentrated in about 15 years.The imaging feaures are mixed bone destruction and more bone is swelling and permeability damage,soft tissue mass is larger,bone tumor is cloudy or acicular,periosteal reaction in a layered and radial,most cases show that the false envelope is not complete.Combined with clinical and imaging examination,the diagnosis of the disease can be made.