In order to further study the temperature field and flow distribution characteristics of plate-fin heat exchanger （PFHE） under the condition of large temperature difference， a joint simulation method based on FLUENT and program based on VC⁺⁺ language is adopted. The simulation method is verified and analyzed by taking a PFHE with a given structure as an example. The results show that the application of the joint simulation method to the simulation of the PFHE is of pratical significane to the study of the temperature field characteristics of the aviation precooler. The error between simulation results and experimental data is 0.6%—6.4%. And the joint simulation method is accurate and feasible. The lateral temperature change in the same channel of the PFHE and the distance from the cold side entrance are close to linear distribution. The outlet temperature of the hot-side core presents an uneven distribution with a large temperature gradient under the superimposed influence of uneven flow distribution and the flow direction of the cold side. The research method is universal and can provide a reference for the simulation of other heat exchangers.