Abstract: A new program was developed to predict the pressure,temperature and mass flow rate of the flow in engine.The air system was simplified into a fluid network comprised of nodes and elements.One-dimensional conservation equations were solved by a method of combination of pressure-correction method,fluid-thermal coupled method and coefficient-correction method.The program was validated through a model with an empirical formula,and the results showed good agreement with the empirical formula.Then the program was used to verify and improve the preliminary design scheme of a jet engine.Results show that the adjusted design parameters obtained with the help of simulation results are satisfactory.