Objective: The aim of this study was to investigate the accuracy of cone-beam computed tomography (CBCT) to assess the volume of bone graft in alveolar cleft patients., Materials and Methods: Twelve patients of unilateral alveolar cleft were included in this study. All patients were taken CBCT preoperative and 1 week postoperative. The digital imaging and communications in medicine (DICOM) files were imported into Simplant software and three-dimensional (3D) reconstruction of the alveolar defect was achieved. With 3D volumetric measurements module, the volume of alveolar cleft was calculated preoperatively. During operation, the syringe compression method was adopted to calculate the actual amount of bone graft. One week postoperative, CBCT scan was performed again to measure the bone volume grafted to the defect. The volumetric ratio of the syringe compression method to preoperative CBCT assessment and the volume difference between syringe compression method and postoperative CBCT assessment were analyzed to evaluate the accuracy of CBCT measurement., Results: The 3D structure of the alveolar cleft and the boundary of bone graft was clear from CBCT images. The estimated volume of alveolar cleft by preoperative CBCT scans was 1.06 ± 0.09 cm, and the actual amount of bone graft determined by the syringe compression method was 1.51 ± 0.12 cm. The ratio between the latter to the former was 1.43 ± 0.07. The calculated volume of bone graft by 1-week postoperative CBCT scans was 1.53 ± 0.11 cm, with no significant difference compared with the actual amount of bone graft (P > 0.05)., Conclusions: CBCT was an accurate measurement to calculate the volume of alveolar defect and bone graft in alveolar cleft patients. Preoperative scans could aid in quantitatively determining the bone amount needed to adequately fill the bone defect, and the postoperative scans give accurate follow-up evaluation after surgery.