The invention relates to a wide-angle thermal imaging wireless alarm device of an unattended substation and a working method, wherein temperature alarm of high-voltage electric power equipment of a remote unattended substation is realized. The device comprises a control module and an infrared thermal imaging system, a radio signal transceiving system and an alarm which are connected with the control module, wherein the infrared thermal imaging system comprises an infrared thermal sensor, an infrared thermal imaging wide-angle camera, a drive device, an infrared thermal imaging processor and an infrared thermal imaging display; an infrared temperature-sensing thermal imaging wide-angle camera is connected with the infrared thermal sensor; the drive device controls the infrared thermal imaging wide-angle camera to rotate in a certain angle range; the infrared thermal imaging system performs active temperature-sensing thermal imaging scanning on the high-voltage electric power equipment running outside the unattended substation in a wide-angle manner and in a large area; the infrared thermal imaging processor and the infrared thermal imaging display are mounted in a remote background control room; and the radio signal transceiving system comprises a radio transmitting device and a radio receiving device capable of transmitting and receiving infrared thermal imaging signals.