Objective To improve the accuracy and safety of lateral gap arthroplasty of temporomandibular joint by applying computer -assisted navigation. Methods Seven patients with unilateral temporomandibular joint ankylosis underwent the navigation-guided lateral gap arthroplasty. Preoperative planning was performed to determine the osteotomy line and extent of ankylosed bone to be resected. The data of preoperative planning were inputted into the navigation system. During the operation, the real-time and accuracy of navigation system were observed. Maximum mouth opening was measured and compared preoperatively, intra-operatively and postoperatively. Patients were monitored for complications and signs of recurrence in the follow-ups. Results Preoperative planning was performed successfully at the workstation of navigation system. All navigation-guided lateral gap arthroplasty were completed by using real-time pointer-based or instrument-based navigation. Measurements illustrated that the mean of maximum mouth opening was 7.0 mm preoperatively, 37.9 mm intra-operatively and remained 36.7 mm postoperatively. Follow-up evaluation showed remarkable improvement in function and esthetics, and no complications and signs of recurrence were observed. Conclusion Computer-assisted navigation in lateral gap arthroplasty of temporomandibular joint could improve the accuracy and safety.