Objective To analyze CT and MRI manifestations of the aneurysmal bone cyst and to evaluate the value of its imaging diagnosis.Methods The manifestations of CT and MRI of the aneurysmal bone cyst confirmed by operation or puncture were analysed retrospectively.Results On CT images,there were obvious liqued-liqued level within the lesions in 16 cases,in which,the CT values in up part was lower than that in low part,and there were obvious soft tissue mass in secondary aneurysmal bone cyst.While,on MRI,all lesions appeared obvious liqued-liqued level except one secondary example,and the soft tissue mass of secondary aneurysmal bone cyst was clear showed.Conclusion Most of aneurysmal bone cyst appear liqued-liqued level within the lesions on CT and MRI,it is a characteristic sign,but not the only one.