目的　测量完整人颅骨的上、下项线及枕骨大孔间的距离，为临床应用提供数据。  方法　在113例中国成年人正常、干燥颅骨标本上，取枕外隆突最高点、上项线上枕外隆突最高点左、右两侧旁开1 cm、2 cm各取一点，颅骨后正中线上枕外嵴中点及其左、右两侧旁开1 cm点各取一点，从上、下项线所取测量点向枕骨大孔方向作与颅骨后正中线平行的直线，用游标卡尺测量枕骨上、下项线间及上、下项线分别与枕骨大孔间的弧面、直线、垂直及水平距离。  结果　在后正中线上，上、下项线间的距离最小，直线距离为（18.11±2.99）mm、弧面距离为（19.18±2.83）mm、垂直距离为（11.11±3.44）mm、水平距离为（14.65±3.19）mm，向左、右旁开后除水平距离变小，其余各距离指标变大；枕外嵴中点到枕骨大孔后缘间两点的距离最小，直线距离为（21.73±3.35）mm、弧面距离为（22.74±3.47）mm、垂直距离为（10.69±3.44）mm、水平距离为（19.10±3.35）mm，向左、右旁开后，各距离指标变大。   结论　下项线准确定位是临床操作安全和有效的关键，以枕外隆突和上项线可以确定下项线位置，在后正中线上，下项线距上项线的垂直距离最小，为（11.11±3.44）mm。

Objective　To measure the relevant distance between the superior nuchal line, inferior nuchal line and the foramen magnum,  and provide the clinical application with scientific and reasonable data.　Methods　The following points in 113 cases of normal and dry skull specimens of Chinese adults were selected: the highest point of the external occipital protuberance and points 1cm and 2 cm left and right on the superior nuchal line; the middle point of the occipital crest and points 1cm  left and right on the inferior nuchal line. Straight lines from those selected points to the foramen magnum parallel to the skull posterior median line were drawn. Measure of the arc distance, straight distance, vertical distance and horizontal distance between the superior nuchal line and the inferior nuchal line,the superior nuchal line and the foramen magnum, the inferior nuchal line and the foramen magnum were made with an ordinary vernier caliper.　Results　The distance between the superior nuchal line and the inferior nuchal line was minimum in the posterior median line. The values of its straight distance, arc distance, vertical distance and horizontal distance were（18.11±2.99）mm,（19.18±2.83）mm,（11.11±3.44）mm and（14.65±3.19）mm respectively. The horizontal distance to the left or right diminished, but the other distances increased.  The distance between the midpoint of the occipital crest and the foramen magnum was minimum. The values ofits straight distance, arc distance, vertical distance and horizontal distance were（21.73±3.35）mm,（22.74±3.47）mm,（10.69±3.44）mm and （19.10±3.35）mm respectively. The distances to the left or right lengthens increased.　Conclusion　The location of the inferior nuchal line is the key to ensure the safety and effectiveness of clinical practice. It can determine the location of the nuchal line with the help of the external occipital protuberance and the superior nuchal line. In the posterior median line, the distance between the superior nuchal line and the inferior nuchal line is minimum, and the number is (11.11±3.44)mm.