A tunnel kiln includes preheating, firing and cooling zones and there is provided a method for controlling the preheating zone. The method comprises forcedly blowing air from the entire ceiling portion of the kiln at the preheating zone in the downward direction to diffuse the hot combustion gas present in the upper portion to the lower portion of the preheating zone, thereby reducing a difference in temperature between the upper and lower portions of the preheating zone. Air may be blown into the preheating zone at a flow rate determined depending on the quantity of the combustion gas within the preheating zone of the kiln.