Abstract: A numerical simulation was employed to study the flow and temperatare fields of hot exhaust gas mixing with cold air in exhaust ejector.In the calculation the algebraic stress model (ASM) with the effect of buoyancy forces as turbulence model was adopted.Four heat radiation flux model was taken as heat radiation model.Due to complicated geometry of the nozzles the boundary fitted curvilinear coordinates were employed and curvilinear mesh was generated with the help of TTM method,then the blocks were put together under the given boundary conditions.A new general numerical method is developed on the basis of SIMPLE (Sami-Implicit Method for Pressure Linked Equations),and a general software was compiled in the boundary fitted curvilinear coordinate system.This software can be used widely for numerical simulation of flow fluid,heat and mass transfer,combustion,radiation in mixed flow with arbitrary boundary shapes.The results for some aeroplanes illustrate that the double convergent walls of the nozzles can intensify the mixing of hot and cold flows,and the violent mixing can greatly reduce the heat radiation flux and the temperature of aeroengine exhaust gas in double convergent nozzles.