There is a guide plate at the upper part in the kiln, which parallel with the upper cover plate, the guide plate shorter than the depth of kiln, that means it left air-vent both ends, the guide plate separate kiln in two parts, upper side is the fan room which lower, down side is the drying room which higher. The cycling fan installed in the middle of the fan room, and multiple paralleling as usual.The heater installed in two sides or one side of the fan room, the wind made by fan pass through the heater to heat, then enter into the space of timber from one side, flow through the timber for heat exchange, makes the timber heated warming, and take away the moisture steam from the timber surface, flowing from the other side of the timber, pass through the other side of the vents flowing into the air inlet port of the fan, forming circumstance airflow in the kiln, made the timber heating and warming constantly.