Airflow in an avian respiratory system was simulated to study why birds affected with airsacculitis have respiratory distress. The airflow in the avian lung was modeled with a 1D electrical circuit and simulated for investigating what effect an increase in wall thickness of air sacs caused by airsacculitis has on flow in lung. The results demonstrated that thickening of the air sac wall caused anti-synchronization between an elastic recoiling force of the air sac walls and an intra-pleural pressure, bringing difficulties in expansion of air sacs to draw in airs during an inspiration period and thereby decreasing air to be pumped out during an expiration period. This was reflected in a decrease in air flow volume in parabronchi where gas exchange takes place. Therefore, it was concluded that airsacculitis causes imbalance in air flow dynamics in the avian lung and thus impairs breathing ability of birds.