Abstract： Background Variations in position and relationship between the internal jugular vein (IJV) and the common carotid artery (CCA) may lead to inadvertent artery puncture which could be disastrous during central venous access. We demonstrated the anatomic relationship of the IJV with CCA in order to find the optimal site and avoid damage of CCA.Methods Two hundred and twenty surgical patients were enrolled. We analyzed the distance and relationship between the IJV and CCA at three cross sections (upper border of the thyroid cartilage, cricoid cartilage and second tracheal ring) by ultrasonography and then measured the diameters of the IJV and CCA and the distances from the IJV and CCA to the skin.Results Twenty patients were excluded on the basis of exclusion criteria. From up to down at bilateral neck, the IJV became gradually more superficial while the CCA became deeper. The diameter of the IJV became gradually larger while that of the CCA gradually smaller. The IJV from lateral to the CCA gradually moved to the front of the CCA, so the percent overlap of the IJV and CCA was gradually increased. Compared with the left side at the same transverse scan level, the distance between the CCA and IJV was wider at the right side and the right IJV was wider. The IJV location in 11 patients was medial to the CCA at one or more transverse scan levels. The angle between the IJV and CCA was significantly small in elderly patients. The CCA had already furcated at the level of the upper border of the thyroid cartilage in seven patients at the right side and in 12 patients at the left side.Conclusions There are variations in the position and relationship between the IJV and CCA. it is relatively more difficult to puncture at the left side of the neck, at a lower position or in elderly patients. On the contrary, it is relatively easier to puncture at the right side, at the level of the cricoid cartilage or in younger patients.