Objective To investigate the clinical effect, safety and technique notes for the 3D navigation-assisted in treating elderly patient with the sacroiliac complex injury. Methods 28 cases of elderly patients with the sacroiliac complex injury （dislocation of sacroiliac joint，Denis I，II area）who had been collected from March 2015 to may 2017 were treated using ISCS with 3D navigation-assisted system. Intraoperative indexes as duration, blooding volume, nerve or blood vessel lesion and postoperative complications were respectively documented. Reduction condition was postoperatively evaluated by Matta radiological criteria, pelvic function was assessed by Majeed scoring criteria at the last follow-up. Results 28 cases with 39 screws in all were placed without neurovascular complications. Each screw averagely took 41.5±4.3 mins with bleeding of 10 - 25mL; 2 patients with Morel-Lavallée injury underwent open debridement and VSD(vacuum sealing drainage). 1 screw moved backward for 1 cm at the 1st month of follow-up, and this abnormal process was controlled by the reasonable intervention. Matta radiological evaluation presented the excellent rate with 89.3% including excellent in 12 cases and good in 13 cases. All patients were followed up for 12.5±2.3 months. The Majeed standard of pelvic function evaluation in the last follow up showed the excellent rate with 92.9%, including excellent in 15 cases and good in 11 cases. Conclusions It can concluded that elderly patient, although, always suffers osteoporosis, 3D navigation-assisted percutaneous ISCS could effectively treat the sacroiliac complex injury and firmly provide an accurate, safe and minimally invasive fixation.