The air heater is an electric heating device which mainly heats the gas stream. The heating element of the air heater is a stainless steel electric heating tube, and the inside of the heater is provided with a plurality of baffles (baffles) to guide the gas flow and prolong the residence time of the gas in the cavity so that the gas is sufficiently heated so that the gas Heating evenly, improve heat exchange efficiency. Air heater heating element Stainless steel heating pipe, is installed in the seamless steel pipe heating wire, filled with a good part of the thermal conductivity and insulation of the magnesium oxide powder after the shrinkage made. When the current through the high temperature resistance wire, the heat generated by the crystallization of magnesium oxide powder to the surface of the heating tube, and then passed to the heated air to achieve the purpose of heating.