The purpose of this study was to compare the clinical outcomes of ultrasonic surgery to the conventional bone cutting technique using bur and saw for the release of ankylosis of temporomandibular joint. We conducted a prospective cohort study on 25 patients with 38 ankylotic joints at Chinese PLA General Hospital from March 01, 2012 to March 01, 2016. Patients were followed up at least 2 years postoperatively. The primary outcome was the intraoperative blood loss per joint. The secondary outcome was the long-term (≥2 years) improvement of maximum mouth opening. The blood loss was significantly reduced in the ultrasonic group compared to the conventional group (107.3 ± 62.3 ml vs. 186.3 ± 92.6 ml, P = 0.019). The long-term improvements of maximum mouth opening were substantial and stable in both groups (33.5 ± 4.8 mm in the ultrasonic group vs. 29.2 ± 6 mm in the conventional group, P = 0.06). Multivariate linear regression analysis showed a significant association between blood loss and technique used (coefficient: 66.3, 95% confidence interval: 22.1,110.4, P = 0.006). The ultrasonic surgery was associated with less intraoperative blood loss when compared to the conventional method for the release of ankylosis of temporomandibular joint while providing a stable and comparable long-term improvement of maximum mouth opening.