The airside heat transfer is a major problem that restrains the development of fin-and-tube heat exchanger，on which the airflow within the space in the unit of fan and heat exchanger has significant influence.In this study，the interior airflow of a U type fin-and-tube heat exchanger is investigated numerically and experimentally.Fluent code is used to simulate the flow in the space and air velocity distribution in the whole field is obtained.Experiment is conducted by using dry ice and a smoke generator is used for fluid flow visualization.The numerical results for the air velocity distribution at different height agree well with the experimental measurements.The velocity in front of the fan is the highest and the heat transfer in this area is stronger.The results provide data for optimization of fin-and-tube heat exchanger and a new ideal for designers in this field.