Irreducible atlantoaxial rotatory fixation (IAARF) often requires surgical treatment. Transoral unlocking the facet joints is a key measure for the treatment of IAARF. We investigate a novel method for treating pediatric IAARF by unlocking facet joint through transoral appraoch and fixed with slim-tarp plate in same stage with same approach. The objective of this study is to investigate the method and efficacy of a unique transoral approach to unlock facet joints and fixation with slim-shaped transoral anterior reduction plate (slim-TARP) plate in the treatment of IAARF. Fifteen patients diagnosed with AARF were transferred to our hospital. After 1 week of bidirectional cervical cranial traction, they were diagnosed with irreducible AARF that, and then underwent transoral release and fixation with slim-TARP plate procedures. Postoperative computed tomography and magnetic resonance were used to evaluate the reduction effect, bone fusion, and fusion time. Japanese orthopaedic association scores were used to compare the recovery of spinal cord function in patients before and after surgery. Complications such as wound infection, neurovascular injury, and loosening of internal fixation were evaluated too. All 15 patients underwent transoral unlocking facet joint and fixation with slim-TARP procedures smoothly. The operation time were 129.2±11.9 minutes, blood loose were 83±23 mL. There were no neurological injury, wound infections, verified or suspected vertebral artery injury, etc. All patients were followed up for a mean of 17.8±6.6 months (range: 12 to 36 mo). Bony fusion was achieved in all patients. Mean fusion time was 3.6±1.2 months (range: 3 to 6 mo). Complete correction of torticollis was achieved in all 15 cases. Preoperative symptoms of neck pain and limitation of neck movement were effectively alleviated at 3 months after surgery. The 3 patients with preoperative neurological deficits had significant relief after surgery, and their latest follow-up results showed that their Japanese orthopaedic association scores increased from 13.0±1.0 to 16.3±0.6. Transoral release and fixation with slim-TARP plate by transoral approach is a feasible and safe method for treating pediatric irreducible atlantoaxial rotatory fixation.