The invention provides an ignition judgment system with a flame sensor replaced with a diesel engine intake air heating device. The ignition judgment system comprises a microcontroller and a 24V powersource. A PWM output port of the microcontroller is connected to an electric heating plug through a power driving circuit, and the power driving circuit converts PWM control signals output by the microcontroller into PWM power signals applied to the electric heating plug. The 24V power source is connected to the power driving circuit through a sampling resistor, and the 24V power source is connected to an input port of an A/D channel 2 through a voltage sampling circuit. An input port of an A/D channel 1 of the microcontroller is connected to a current sampling circuit, and an input port of the current sampling circuit is connected with the sampling resistor in parallel. According to the ignition judgment system with the flame sensor replaced with the diesel engine intake air heating device, a software and hardware combining method is adopted through the microcontroller to judge the ignition state of a diesel engine instead of the flame sensor, the intelligent degree is high, and costis low.