The numerical simulation of three dimensional internal and external flows for non-vectoring two-dimensional nozzles with or without trailing edge modification was conducted by means of time marching finite volume method.The difference between the modified and unmodified nozzle was found.Two couple of counter-rotating streamwise strong vortices which can enhance the jet flow mixing appeared around the modified nozzle trailing edge.And these induced vortices have greater effect on temperature distribution of the exhaust plume.The result of this research shows that the design of trailing edge modification can evidently reduce the length of high temperature domain of the exhaust plume and may be benefit to the reduction of infrared radiation.