The invention relates to a hot air processing device for liberibacter asiaticus comprising a transport vehicle, a processing cover, a control mechanism group, a heating device, a power supply device and a base; the base is mounted on the transport vehicle; the control mechanism group which is used for driving the processing cover to rotate, elevate or descend, and horizontally move is mounted on the base; the processing cover is mounted on the control mechanism group; the heating device which is used for providing hot air to the processing cover is mounted on the transport vehicle; the power supply device which is used for providing electric power to the hot air processing device is mounted on the transport vehicle; a blower is connected with a heater; the processing cover is provided with an air inlet and an air outlet; the heater is connected to the air inlet of the processing cover through an air inlet pipe; the blower is connected to the air outlet of the processing cover through a backwind pipe. The invention also relates to an application method of the hot air processing device. By means of the method and device, air can be heated and then is used for quick heat treatment on trees having liberibacter asiaticus in the adult-plant stage; the invention belongs to the technical field of plant protection.