This paper presents an energy efficient ventilation method—dam tunnel air handling for hydropower station ventilation. The heat transfer characteristic between supply air and the dam tunnel is studied by model experiment. Supply air velocity, air temperature and dam tunnel surface roughness are chosen as the mainly influencing factors, the air temperature distribution along airflow direction are measured and analyzed in detail. The results show that the heat transfer performance in dam tunnel is improved as the increased of supply air temperature and the dam tunnel surface roughness, or maintained the supply air velocity at a lower level. This experimental study and its results are helpful to develop alternative and efficient systems for hydropower station ventilation.