A modular modeling method for air system with fast transient was established. The air system model was decomposed into four kinds of basic units interconnected by the standard data interface

which accounts for combined effects of volume packing and flow inertia during rapid transients. The numerical code was programed by utilizing object oriented technology

and its predictions were validated against published data. The results show that the simulation model accurately predict the millisecond time scales physical phenomena of air system with fast transients

such as reversal flow

transmission of pressure wave

coupled oscillations between multiple cavities

etc. Moreover

its modular charicteristic allows integration of further detailed air system units and establishment of more complex air system network. The modularized simulation method has prospect in studying the complex dynamic characteristics and mechanism of aero-engine air system.