The invention provides a diesel engine plateau cold-start preheating method. The diesel engine plateau cold-start preheating method comprises the following steps that after a diesel engine electroniccontrol system is powered on, whether the smaller one of the coolant temperature and the inlet air temperature is lower than -5 DEG C or not is judged, and if yes, inlet air preheating needs to be conducted; a preheating plug is controlled to conduct inlet air heating according to the preheating duration inquired by an MAP picture in the premier preheating process; after premier preheating is completed, a prompt is given, starting is waited, time is recorded for a certain period of time to wait for starting, when the rotation speed meets the starting requirement, waiting is stopped, and the later preheating process starts to be performed. According to the diesel engine plateau cold-start preheating method, an inlet air preheating strategy under the cold-start working condition is built byutilizing a few of environment variables, the preheating process is divided into the singular inlet air hating stage before starting and the inlet air heating stage cooperating with fuel oil injectionafter starting according to the engine state, and the whole preheating process is optimized and accelerated; and through the strategy, under the condition of the limited computing resources distributed by a single chip microcomputer, the preheating process under the plateau extreme environment of which the lowest temperature is -30 DEG C is quickly and effectively controlled in real time.