目的　通过对骶髂关节三维重建模型进行解剖参数测量和虚拟骶髂螺钉固定，明确骶髂螺钉的最佳进钉点和安全置钉范围。   方法　用Mimics软件对50例骨盆CT数据进行三维重建，切割出骨盆三维模型，测量S1椎体解剖参数,在同一骶髂关节多次虚拟置钉，确定螺钉最佳进钉点，计算其安全角度。三维重建骨盆表面软组织，确定髂前上棘顶点N、髂嵴上点M、进钉点P的体表投影点N1、M1、P1，分段测量各投影点之间的长度。   结果　骶骨Ⅱ区中心螺钉骨面进钉点P到髂前上棘顶点N的距离PN男性为（95.17±5.59）mm, 女性为（98.49±7.71）mm; 经点P作PN的垂线与髂嵴交于点M，PM长度男性为（58.71±4.33）mm，女性为（54.59±6.01）mm；从髂前上棘顶点N沿髂嵴到点M的长度男性为（129.78±6.25）mm，女性为（130.64±7.79）mm，其中男女间PM长度有显著差异。中心螺钉前、后倾安全范围男性为（10.70±2.00）°，女性为（7.20±1.64）°；头、尾倾安全范围男性为（12.36±2.68）°，女性为（11.27±3.29）°，男性前、后倾安全范围明显大于女性。男女间体表投影点之间的长度仅P1M1有显著差异。   结论　通过触摸髂前上棘顶点N和髂嵴上的点M，可确定骶骨Ⅱ区骨折固定螺钉的体表进钉点。以S1椎体上表面为横截面，后表面为冠状面，男性螺钉前后倾安全范围约10°，头尾倾安全范围约12°，女性前后倾安全范围约7°，头尾倾安全范围约11°。

Objective　To identify the best entry point of the sacroiliac（SI）joint screw  and safe angle by measurement of anatomical parameters of S1 vertebrae and virtual screws fixation of the SI joint in the three-dimensional reconstruction pelvic model.　Methods　50 pelvis including 25 females and 25 males were reconstructed in Three-dimensional form and cut by Mimics software. The anatomical parameters of S1 vertebrae were measured and the virtual screws were placed in each SI joint through different entry points, then the best entry point of the screw was identified and the safe angles of the screw were calculated. The surface soft tissues of the pelvis were reconstructed in three-dimensional form by Mimics software , the surface projection points of entry point P, anterior superior iliac spine’s vertex N, point M were P1, N1 and M1, respectively, and the lengths of P1M1,P1N1 and M1N1 were measured sectionally. 　Results　The lengths between central screw’s entry point P and point N were（95.17±5.59）mm (male) and（98.49±7.71）mm (female). PM was vertical line of PN passing point P and point M was intersect point of iliac crest and PM, the length of PM was（58.71±4.33）mm (male) and（54.59±6.01）mm (female). The distance from point N to point M, which were along the iliac crest, were（129.78±6.25）mm (male) and（130.64±7.79）mm (female). The difference of PM’s length between male and female had statistical significance (P＜0.05) . The central screw’s safe ranges in the forward and backward incline were (10.70±2.00) °(male) and (7.20±1.64) ° (female),and the safe ranges in the cephalic and caudal incline were (12.36±2.68) °(male) and (11.27±3.29) ° (female). The forward and backward incline safe ranges showed statistical difference between male and female (P＜0.05). The length of P1M1 was significantly different between male and female (P＜0.05).  Conclusions  The best entry point of the SI joint screw was determined according to the projection points of anterior superior iliac spine’s vertex N and point M , the screw’s forward and backward incline ranges is about 7°（female） or 10°（male）,the cephalic and caudal incline ranges is about 11°（female）or 12°（male） When the top surface and the posterior surface of S1 vertebrae are regarded as the transverse plane and the coronal plane respectively.