The invention discloses a double-channel preheating device used for cold starting of a diesel engine, and belongs to the technical field of diesel engines. The double-channel preheating device used for cold starting of the diesel engine comprises a smoke discharging channel, a heating cavity, a cooling liquid channel and a diesel channel, wherein the heating cavity makes contact with the smoke discharging channel to achieve indirect heat exchange, the cooling liquid channel and the diesel channel make contact with the heating cavity to achieve indirect heat exchange, a water injection port andan exhaust port are formed in the upper portion or the top of the heating cavity, and a heating medium part used for filling calcium oxide powder is arranged on the lower portion of the interior of the heating cavity. According to the double-channel preheating device used for cold starting of the diesel engine, heat generated by calcium hydroxide formed through the chemical reaction between the calcium oxide powder and water is used for heating engine cooling liquid and diesel, so that rapid starting of the diesel engine in a low-temperature environment is achieved; the calcium hydroxide is dried under the continuous high-temperature effect of high-temperature smoke of the engine so as to be decomposed to generate calcium oxide again, so that consumption of extra electric energy or fuel is not needed, and configuration of power lines, control circuits and programs is not needed either; and the double-channel preheating device used for cold starting of the diesel engine is simple in structure, easy to maintain, low in cost, capable of saving energy and environmentally friendly.