Abstract: Transverse smoke extraction tests were carried out in a reduced scale channel model. The configuration characteristics of the smoke-air layer interface, the maximum temperature rise of smoke layer and the horizontal spreading velocity of smoke flow were investigated under different extraction rates. The results show that the smoke layer maintains good stratification under a small extraction rate, whereas mixing is intensified between the upper smoke layer and lower ambient air with the increase of the extraction rate. Stronger mixing is found at the location near the channel portal. It is found that both the normalized maximum temperature rise and the horizontal spreading velocity decay exponentially with extraction rates, which both decay faster at the location near the channel portal. The difference between the spreading velocities at locations near and far away from the portal becomes larger with the increase of extraction rate.