The embodiments of the invention disclose an infrared thermal imaging online monitoring method and system. The method includes a thermal image acquisition step, a model generation step, and a thermalimage analysis step. In the thermal image acquisition step, a thermal image is acquired from infrared thermal imaging equipment connected, and the thermal image and the parameters thereof are saved toa database, wherein the parameters at least include the equipment parameters of the thermal imaging equipment, the temperature values corresponding to the preset pixels in the thermal image, and environment data. In the model generation step, a heat map management table, an equipment-heat map correspondence table, a heat map warning table and an equipment alarm analysis table are generated. In the thermal image analysis step, the thermal image and the temperature values corresponding to the pixels in the thermal image are acquired from the database, the maximum temperature of a whole heat mapis calculated, the maximum temperature in the region is calculated according to the position of the equipment in the heat map, and the maximum temperature is compared with the warning threshold and the equipment threshold corresponding to the thermal image in the heat map warning table and the equipment-heat map correspondence table generated by a model generation module to determine whether or not to give an alarm.