Objective To evaluate spiral CT and three dimensional reconstruction in the diagnosis of severe renal trauma in children. Methods 4 children were taken spiral CT one month after injured in car accidents.Picker CT Twin is used to scan kidney and ureter,including plane scan and contrast enhancement nephrography. Pitch 1.0 and slice thickness 6.5 mm were selected.MPR,MIP and 3D reconstruction were used as postprocessing. Results Of the 4 cases,2 cases had laceration of right kidney and UPJ avulsion,1 case a completely amputated lower pole of left kidney and 1 case a UPJ avulsion in right ureter. Giant urine cysts could be found in all the 4.The CT findings were confirmed by operations. Conclusions Spiral CT and 3D images could accurately depict the condition and severity of injuries of kidney and ureter.The 3D images depict the injuries and surounding structures from various directions,so that the optimal kind of operation could be selected with the reference of images.