Abstract: Objective To evaluate the influential factors of relationship between internal jugular vein (IJV) and common carotid artery (CCA) by ultrasonography in order to increase the success rate of puncture. Methods One hundred and fifty elective surgical patients in our hospital from January to June in 2014 who required central venous access were included in this study. The angle between IJV and CCA and the overlap of CCA at the apex of triangle formed by sternocleidomastoid muscle at 0°, 30°, 60° and maximum head rotation were analyzed by ultrasonography. The effects of age, gender and body mass index (BMI) on the CCA overlap were also analyzed. Results With the increased head rotation, the IJV moved from the lateral to the front of CCA, so the angle between IJV and CCA became smaller (P< 0.01) and the percent overlap of CCA and IJV were gradually increased at both sides (P< 0.01). Compared with the left side at the same degree of head rotation, the angle between IJV and CCA was greater and the percent overlap of CCA was lower on the right side (P< 0.01). Female and elderly patients were associated with more overlap of CCA at head rotations of 0° or 30° (P< 0.05). The overlap rate of CCA in high BMI patients at any head rotations were higher than that of low BMI patients (P< 0.05). Conclusion The relationship between IJV and CCA changes with head rotation and is easily influenced by age, gender and BMI. Head rotation should be limited to 30° when using the anterior or central approach and head should be rotated to maximum degree when using posterior approach in order to avoid inadvertent puncture of CCA.