This study investigated upper airway aerodynamic characteristics of patients who underwent maxillectomy using three-dimensional reconstruction and computational fluid dynamics. The results revealed the generation of low-velocity vortices throughout the entire maxillary defect during respiration. The nasal structure on the nonsurgical side changed postsurgically, possibly due to the pressure gradient between the defective and healthy side. The bilateral disturbed airflow patterns are believed to be the cause of common symptoms. The numeric simulation technique could be used as a potential method to understand upper airway morphology changes and respiratory functions, thus guiding the fabrication of prostheses.