目的·建立中国18~25岁颜面协调汉族人群Downs分析法头影测量正常值，并分析其性别特征及地域特征。方法·采用分层抽样，在中国7个自然地理区域分别进行受试者招募，筛选3万余人，最终共纳入883例符合要求的颜面协调者。收集受试者的基本资料，拍摄头颅定位侧位片，采用Downs分析法（使用解剖耳点）测量硬组织数据，并比较牙颌结构的性别差异及地区差异。结果·颌凸角、上下牙槽座角、下颌平面角以及平面角，这4项硬组织指标的性别差异具有统计学意义（P<0.001）。其中女性颌凸角、下颌平面角、平面角皆大于男性，上下牙槽座角小于男性；上下中切牙角、下中切牙-平面角、下中切牙-下颌平面角及上中切牙凸距这几项牙性指标的性别差异无统计学意义。Downs分析法10项指标的测量结果皆显示出地区差异，但部分地区之间也有共通特征。东北、华东、华南三个沿海地区的面角较小，下颌平面角、颌凸角、平面角及上中切牙凸距偏大，即相较于内陆地区，沿海地区的颜面协调者颏部靠后，下颌陡度更大，上前牙位置更靠前，硬组织轮廓有更凸的倾向。结论·中国颜面协调汉族成人牙颌结构存在性别差异，且该差异主要表现在骨组织指标上。各地区有独有的牙颌特征，也有部分共同特征。临床诊疗需考虑到这些特点以制定个性化治疗方案。

Objective ·To establish Downs cephalometric norms for the Han Chinese aged 18‒25 with harmonious faces, and to analyze gender and regional characteristics. Methods ·A stratified sampling approach was used to recruit participants from seven geographic regions across China. Over 30 000 volunteers were screened, and 883 participants with harmonious faces were ultimately included. Basic demographic data were collected, and lateral cephalometric radiographs were taken. Hard tissue measurements were performed with Downs analysis (using anatomical porion). The data were then statistically analyzed to compare gender and regional differences in dentofacial structures. Results ·The gender differences in the four hard tissue measurements, the angle of convexity, A-B plane angle, mandibular plane angle, and occlusal plane angle, were statistically significant (P<0.001). Females showed larger values for the angle of convexity, mandibular plane angle, and occlusal plane angle, but smaller values for the A-B plane angle, compared to males. The gender differences in the interincisal angle, L1 to occlusal plane, L1 to mandibular plane, and U1 to AP plane were not statistically significant. There were regional differences in all 10 measurements of Downs analysis, though some regions shared common features. Specifically, the northeastern, eastern, and southern coastal regions exhibited a smaller facial angle, and larger mandibular plane angle, angle of convexity, occlusal plane angle, and U1 to AP plane. It suggested that, compared to inland regions, individuals from coastal regions tended to have more retrusive chins, steeper mandibular planes, more prominent upper incisors, and more convex hard tissue profiles. Conclusion ·Gender differences exist in the dentofacial hard tissue structures of Han Chinese adults with harmonious faces, primarily in skeletal measurements. Each region has its unique dentofacial characteristics, along with some common features. These differences should be taken into account in clinical diagnosis and treatment for the development of personalized and precise therapeutic strategies.