Objective To study the airflow characteristics in lower respiratory tract of acute respiratory distress syndrome (ARDS) patients with different degrees of respiratory distress by using computational fluid dynamics (CFD) technology. Methods Three-dimensional model of lower respiratory tract from a healthy subject was established based on CT image data. Standard k-ε turbulence model was used to simulate the airflow in lower respiratory tract, and the distribution characteristics of air velocity, airflow rate, air pressure and wall shear stress (WSS) in lower respiratory tract were analyzed. Results The function relationship between the pressure drop of airflow in lower respiratory tract and the respiratory intensity was fitted. The distribution characteristics of air velocity, air pressure and WSS in lower respiratory tract were obtained, and the airflow distributions in the lungs and the bronchi of each lobe were also obtained. Conclusions More detailed data of lower respiratory airflow field can be obtained by CFD simulation analysis, which provides the theoretical basis for clinical treatment of ARDS patients.