To explore the value of imaging in the preoperative evaluation of pygopagus conjoined twins (PCT), and analyze the significance of imaging for separation surgery plan and prognosis.Imaging data of a case with PCT, including ultrasound, X-ray, CT, MRI were collected from the case with PCTs treated in our hospital. The features of the images were analyzed for identification of the conjoined region, size, and structures and for judgement of other organ malformation and general body state.The conjoined region located at the lumbosacral spine of which anteroposterior diameter was 7.9 cm, and 6.0 cm for cranial-caudal diameter. Spina bifida were found below L3 in bilateral twins. There were no bone structures but cartilage fusion in spine and pelvis. The neural structure such as spinal cord and cauda equina, lower GI tract and anus, and urinary tract were separated. The dural sac were fused. There were cryptorchidism in one twin, patent ductus arteriosus in both twins. The intraoperative finding matched with imaging results. Crossing V-shaped skin flap was used to cover the wound surface. The dura of conjoined twins were sutured. Successful separation of the PCT was achieved. There were no complications of infection, cerebrospinal fluid leakage and neurological deficit. The healing of the skin flap was good. With 6 months follow-up, the growth and neurological function were normal.Imaging methods were selected according to the type of conjoined twins and the clinical symptoms and signs. The radiologic investigation can reveal the structure and size of conjunction area. Imaging investigation has important significance for the prediction of difficulty in surgery, selection of surgical procedures, and evaluation of prognosis.