To improve the calculation accuracy for the heat exchanger, this paper establishes a compressible flow model for the pressurized air side of the exchanger. Considering the heat exchanger in wheel type loader, the present model employs the change rate of cross-section, heat transfer amount and surface friction coefficient as variables. CFD(computational fluid dynamics) is used to validate the model and simulation results have shown that the deviation between the present compressible flow model and the traditional incompressible model increases with the increasing flow rate. Compared with experimental tests, the incompressible model predictions are only acceptable when the flow rate is low; whereas the present compressible model provides more accurate predictions for high flow rate zone. Results reveal that the maximum deviations between the present model and test on pressure and temperature are merely 6.5% and 7.5%, respectively. Therefore, the present model solves the problem of simulating the high flow rate zone due to the neglect of the compressibility. This model would further guide the optimal design of heat exchanger.