Computational fluid dynamics (CFD) allows the visualization and understanding of physics of flow associated with stent implantation. This study uses patient computed tomography (CT) images to investigate the relationship of pressure drop and air flow rate in the tracheal airway. Moreover, the cross-sectional areas of the patient airway were measured and the area stenosis ratios were calculated. The stenosis ratios were 75.64% and 38.08% without and with stent treatment, respectively. Simulation results show that at an air flow rate of 30 L/min, the pressure drops between the inlet and the outlet before and after central airway stent implantation for the inspiratory phase were 77.23 and 7.05 Pa, respectively. The improvement gain (IG) was 9.95. The IG increased with increasing air flow rate. At an air flow rate of 120 L/min, the value of IG was 11.68. A higher IG value indicates lower airway resistance after an airway stent implantation. The CFD numerical results demonstrate the feasibility of computing airway resistance based on CT images. In clinical practice, it is difficult to assess patients with severe airway obstruction using a symptoms score or a pulmonary function test due to their critical condition. The proposed noninvasive approach for determining airway obstruction severity is helpful for patients who are unable to do pulmonary function tests.