The invention relates to the field of domestic waste drying treatment and in particular relates to a method for heating domestic wastes by hot air to evaporate moisture and a drying device of the method. The method is characterized in that the domestic wastes are continuously heated and the temperature of the domestic wastes is kept in the range of 100-270 DEG C for evaporating the moisture in the wastes. The drying device comprises a rotary kiln provided with a heating device in the length direction. According to the method, the domestic wastes are continuously heated to evaporate the moisture in the wastes, the obtained dried wastes can be gasified to prepare fuel gas, and the problem that a gasification furnace cannot keep normal operation when non-dried wastes are put into the gasification furnace to prepare the fuel gas is solved. According to the drying device, on one hand, the domestic wastes can be uniformly dried after being put into the rotary kiln by continuous rolling of the rotary kiln; on the other hand, the heating device is added to the rotary kiln in the length direction, so that the whole rotary kiln is in a continuously heated state, and the wastes are continuously heated during rolling for evaporating the moisture in the wastes and are gradually dried.