The atrium is often designed in the center of high-rise residential building, and it is more like a light well without ceilings or floors from the bottom to the top. The stack effect of the atrium was mainly used to provide natural ventilation and passive cooling, however, there are many factors for the airflow and the characteristics of the atrium are complex. In this study a 10-storied residential building model has been employed to clarify the ventilation characteristics of the atrium and the rooms, which were effected by the different forms of lateral openings. The experiment was conducted under the effect of thermal buoyancy, and the similarity requirements were satisfied. At the same time, the prototype building was simulated numerically on the conditions. Results showed that high-rise residential buildings with atriums are at an advantage for the buoyancy-driven ventilation in lower part rooms and at a disadvantage for the upper part rooms. The enlargement of the numbers of opening floors causes the increase of the airflow rate through the atrium and the decrease of airflow rate through each floor. When the opening floors are evenly distributed along the building, the enlargement of the numbers of opening floors causes the increase of the temperature in the building at almost all heights, and an increase in temperatures with the height H can also be seen in the building.