The utility model relates to an improved air pre-heater which is composed of a fume inlet, a fume outlet, an air inlet, an air outlet, a fume box, an air collecting box and a main box body, wherein the main box body is provided with a heat conductive pipe of which the outer wall is provided with a plurality of fins which have two different heights and are arranged in a high and low mode. The improved fins can aggravate the disturbance of the fume, enlarge the convective heat conductive coefficient of the fume and the fins, and reduce the sedimentation and the erosion of fume spot. The heat conductive pipe is provided with turbolator insets with different length or sectional arrangement. Turbolators with different length or sectional arrangement can greatly reduce the flow resistance of air when the heat conduction in the pipe is enhanced, and the heat exchange of the fume and the air are strengthened to the maximum.