Objective：This study aims to explore the feasibility，safety，efficacy and medium-term outcomes of 3D printed customized porous titanium acetabular prosthesis in treating acetabular bone defection. Methods：Twelve patients with acetabular bone defection［8 male and 12 female，with a mean age of（62.25±12.21）years，range 42-82 years］were treated with 3D printed customized porous titanium acetabular prosthesis from January 2016 to September 2017. The 3D printing techniques was used for reconstructing and designing the optimal acetabular prosthesis for the personalized acetabular bone defection of each patient. The acetabular prosthesis was subjected to porous processing. The 3D printing of porous titanium acetabular prosthesis and post-processing was subsequently performed. The acetabular prosthesis was implanted through the lateral approach of hip joint. The operative duration，intraoperative blood loss and complications were recorded. All patients were followed up postoperatively. Pain was assessed using the visual analog scale（VAS），and the hip joint function was evaluated using the Harris score and gait analysis. The patients underwent anterior-posterior radiography and computer tomography of the hip joint aiming to observe the restoration of lower limb alignment and the position of the acetabular prosthesis. Results：The mean operative duration of 12 patients was（2.23±0.7）h（1.1-3.5 h），and the mean blood loss was（406.67±219.29）mL（150-820 mL）. All patients were followed up for 12 to 26 months，with an average of 15.33 months. All patients were satisfied with functional restoration. The VAS scores ranged from 5.17±1.53 preoperatively to 1.67±0.78 postoperatively（t=9.225，P < 0.001），and Harris scores ranged from 47.67±7.15 preoperatively to 86.75±4.52 postoperatively（t=-27.380，P < 0.001）with statistically significant difference，respectively. The image suggested good restoration of lower limb alignment and position of the acetabular prosthesis，and a close contact between the titanium acetabular prosthesis and acetabular bone defection without loosening. Conclusion：The 3D printed customized porous titanium acetabular prosthesis could reconstruct the defect of acetabular and increase the initial stability of hip joint. The method could reduce the difficulty of the hip reconstruction，and the patients could obtain good hip joint function.