This study mainly investigated the wall temperature affects on the ventilation performance of the UFAD system with multi-zone mode simulation and experiment methods. A room which has dimensions 4.4×2.7×2.5m and consists of a single source of heat and a cooling wall was developed. Laboratory experiments were carried out to measure the air temperature distribution of the main space and the cooling boundary layer under three cases. From the model simulated and the experimental results it is obvious that the stratification in the room disappears as the temperature of the cooling wall decreases, the downdraught generated by the cooling wall reverses with the main zone airflow. The conclusions can provide the guidance on designing the UFAD systems.