Abstract: In order to obtain the influencing factors on the negative pressure flow environment of the large airborne biological isolation cabin and avoid biological leakage during the air transportation process of infectious disease patients, a computational fluid dynamics (CFD) method was adopted to study the influence of factors such as air inlet size, flight conditions, expanded cabins and internal facilities on the pressure difference and air circulation characteristics. The results show that the better control effect for negative pressure can present between the diameter 50～70 mm of air inlet, and the smaller the diameter size sets, the higher the efficiency of negative pressure will produce because of the higher fan power required in large air inlet. The power consumes differently under different flight conditions, i.e. the highest power consumption at the ascending stage of the aircraft, followed by the level flight stage, and finally the descending stage. The expansion of the cabin body and the opening or closing of its connecting cabin doors can impact little on the pressure difference relatively. The internal facilities can also create a certain range of low-speed areas, and affect the air flow.