Reduced-order model of proper orthogonal decomposition method (POD) was established to analyzed performance of fluid flow and heat transfer in flat tube bank fin heat exchanger. Numerical results of POD were compared with those of FVM. It indicates that average relative error between POD results and FVM results is no more than 5.7% while computational speed is improved 164.78-2021 times. Conclusion is of theoretical meaning for optimizing heat exchanger structure and running mode in engineering.