Abstract:[Objective] To introduce the surgical technique and preliminary clinical results of percutaneous cannulated screws under navigation for Day typeⅡcrescent fracture dislocation of the pelvis (CFDP). [Methods] From January 2015 to December 2018, 23 patients received abovesaid surgical treatment for Day typeⅡ CFDP. As Mimics 17.0 software was used to plan screws fixation before operation, an orthopedic 3D navigation was used during the operation. After the screw track was determined, the registration of navigation was completed centering on the sacroiliac joint of the affected side to obtain the relative position of the crescent fracture line passing through the sacroiliac joint. Under navigation, sacroiliac screws were used to fix the sacroiliac joint in front of the crescent fracture, and then LC-Ⅱ screws were placed under the navigation posterior to the "teardrop". Subsequently, the CLIC point was used as the entering point to place the second screw parallel to the LC-Ⅱ screw. [Results] All the 23 patients had operation performed successfully without complications such as neuro- vascular injury. The time for LC-II screw placement ranged from 1.8 min to 3.0 min with an average of (2.3±0.3) min. The Majeed functional score significantly increased 6 months postoperatively compared with that preoperatively [(87.3±1.6) vs (18.5±1.1), P<0.05]. According to Gras classification, the safe screw placement rate was of 95.6% (22/23). In addition, the excellent and good rate of fracture reduction was 91.3% (21/23) based on Matta's imaging criteria. [Conclusion] This percutaneous cannulated screw under navigation for Day type Ⅱ CFDP has the advantages of low radiation exposure, accurate screw placement, satisfactory fracture reduction, and good functional recovery.