Abstract: A new approach combining fluid network and unsteady simulation method was developed to predict the unsteady characteristic of pressure,temperature and mass flow rate of the flow in engine.The fluid system was simplified into fluid network comprised of nodes and branches.Conservation equations were solved by a newly introduced method combining pressure-correctional method and differential method.The program was applied to propulsion test article(PTA) model,which was compared with the empirical correlation and numerically simulated result of general fluid system simulation program(GFSSP) of NASA.The computational results show good agreement with the benchmark.Then the program was applied to the simulation of the jet engine cooling system.