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Background Resuscitative endovascular balloon occlusion of the aorta (REBOA) can timely prevent the wounded from massive hemorrhage. We aim to study whether the combination of the xiphoid process and the umbilicus could guide the placement of REBOA in zone III without fluoroscopy. Methods We conducted a retrospective study in a university hospital that included 57 subjects who underwent contrast-enhanced computed tomography (CT) from April to December in 2019. External distances and intravascular lengths were measured by three-dimensional reconstruction CT images on the workstation, including the distances from the femoral artery to the xiphoid process (FA-Xi), the midpoint between the xiphoid process and the umbilicus (FA-mXU), the umbilicus (FA-Ui), the midpoint of the zone III (FA-mZIII), the lowest renal artery (FA-LRA), and aortic bifurcation (FA-AB). The relationship between external landmarks and REBOA catheter positioning in zone III was studied, involving the quartering distances between the xiphoid process and the umbilicus, the distance below the xiphoid process and that above the umbilicus. The predicted accuracy and safety margin of the balloon (distal and proximal) were calculated by curvature plane reconstruction. The probability of balloon positioning in zone III using these three methods was compared by Chi square test. Results The average length of aortic zone III was 9.4 cm (SD = 10.0), and that of FA-mZIII on the right and left sides were 24.4 cm (SD = 2.1) ,23.8 cm (SD = 2.1), respectively. FA-Xi was significantly longer than FA-LRA, and FA-Ui was significantly shorter than FA-AB (P < 0.05). Using the quartering distances between the xiphoid and the umbilicus, the distance below the xiphoid, the distance above the umbilicus to predict the length of REBOA catheter positioning in zone III showed no statistically significant difference. Using FA-mXU to predict the accuracy of catheter positioning in zone III on the left and right sides were 84.2% and 86%. Although there was a little difference between the left side of FA-mZIII and FA-mXU, there were no statistical differences on the right side. Conclusions The midpoint between the xiphoid process and the umbilicus is a good external landmark to guide the placement of REBOA in zone III without fluoroscopy.