Cross ventilation is one of the most important techniques for achieving energy conservation and for maintaining a comfortable indoor environment in summer. But it is difficult to evaluate the effect of cross ventilation quantitatively and to design based on a quantitative evaluation, because the indoor environment is uneven and changes with the outside conditions under cross ventilation. The full-scale model experiment has been done under cross ventilation, and the properties of airflow in and around the full-scale model have been examined. In this paper, the mixing property and heat exhaust effect of cross ventilation are discussed. Concentration decay in the full-scale model is measured by using tracer gas technique, and the spatial unevenness of mixing property is examined. And it is shown that the different mixing properties are formed with the airflow pattern. In the experiment of the heat exhaust effect, the temperature of air and surface and exhaust heat is measured. The relation between the temperature reduction and the flow path is examined. Two experiments show that ventilation rate is the most effective factor to decide the exhaust heat and the room mean age of air. But air flow pattern also has a influence.