The invention provides an automatic heating device for an agricultural machinery. The automatic heating device for the agricultural machinery comprises the agricultural machinery; and the agriculturalmachinery comprises a cab and an exhaust gas emission pipe which is arranged on one side of the cab. The automatic heating device for the agricultural machinery has the beneficial effects that mechanical vibration of a heat exchanging coiled pipe can be reduced by arranging a shock absorbing sleeve; as the heat exchanging coiled pipe and a heating pipe form a closed circulation loop through a flexible circulating pipe, and the cab is heated by absorbing heat energy radiated by the exhaust gas emission pipe, the automatic heating device is energy-saving and environmentally-friendly; water circulation in the circulation loop can be automatically accelerated by using an arranged circulating pump so that the heating effect is enhanced; and as an arranged exhaust fan can automatically blow theheat radiated by a heating pipe into the cab in the form of hot air, the heating speed is increased, and the heat radiation is more uniform.