目的　研究真空成型袋在盆腔野放射治疗中的价值 ,并比较不同体位固定方式的优劣。方法　 30例盆腔野放射治疗恶性肿瘤患者随机分为 3个组 :不使用体位固定器组、用真空成型袋固定腰部组及用真空成型袋固定双下肢组。拍摄前野和侧野模拟定位片和定位证实片 ,测量解剖参考点和照射野边界之间的距离。结果　与未使用固定器组比较 ,使用真空成型袋可明显减小左右方向、前后方向和三维摆位误差及≥ 5mm三维移位丛集频率 (P <0 .0 5) ,但未减小上下方向的摆位误差 (P>0 .0 5) ;与固定腰部组相比 ,固定双下肢组明显减小了侧野前后方向的摆位误差 (P <0 .0 5)。结论　真空成型袋可减小盆腔野放射治疗的摆位误差 ,尤其是固定双下肢的方法 ,推荐临床使用 Objective To study the value of vacuum forming bag in radiotherapy of pelvic cavity field and to compare the advantages and disadvantages of different position fixation methods. Methods Thirty patients with pelvic field radiotherapy of malignant tumor were randomly divided into three groups: without using the position fixator group, the lumbar group with the vacuum forming bag and the double lower limb group with the vacuum forming bag. Photograph the anteroposterior and lateral field simulations and positioning confirmation tablets and measure the distance between the anatomical reference point and the radiation field boundary. Results Compared with the unused fixator group, vacuum forming bags could significantly reduce left-right direction, anteroposterior direction and three-dimensional setup error and ≥5 mm three-dimensional shift cluster frequency (P <0.05), but did not reduce the up and down direction (P> 0.05). Compared with the fixed lumbar group, the immobilization of both lower limbs significantly reduced the setup error in the anteroposterior direction (P <0. 05). Conclusions Vacuum-formed pouches can reduce the setting error of pelvic field radiation, especially for the fixation of both lower extremities. It is recommended for clinical use