Objective To study the characteristics of upper airway airflow dynamics during inspiration after unilateral total maxillectomy by means of computer numerical simulation. Methods Based on postoperative CT images of three patients with unilateral maxillary tumor, three-dimensional upper airway structures of the patients were reconstructed, and the upper airway airflow was simulated numerically by computational fluid dynamics method. Results The upper airway airflow trends of the patients during inspiration after unilateral maxillectomy were obtained. Airflow in the defect nasal cavity was separated, and made the spacious vortices of low velocity occurred throughout the entire maxillary defect cavity. Conclusions The upper airway trends of the three patients were generally in conformity with each other after their unilateral total maxillectomy, which illustrated that the respiratory patterns of such patients were of universality. Unilateral total maxillectomy resulted in structure changes of patients’ upper airway, which could disturb the upper airway airflow patterns，and affect the physiological functions of patients’ upper airway. Numerical simulation of patients' upper airway airflow after unilateral total maxillectomy could help to explain the phenomena of nasal drying and crusting, secretion accumulation as well as other symptoms of the kind of patients.