A low-temperature environmental line on-line monitor device thermal power generation device relates to the technical field of high-voltage transmission line on-line monitoring, and solves the problemthat the existing power supply can not stably and long-term supply power to the transmission line on-line monitoring device. The two bus plates of the invention are arranged opposite to each other, two wire connecting heads are respectively fixed on the two bus plates, 2N guide bars are arranged between the two bus plates at intervals, the odd plurality of guide bars are fixed on one bus plate atthe same time, and the even plurality of guide bars are fixed on the other bus plate at the same time; two adjacent guide strips are arranged as a group of guide channel, on Multiple power generationmechanisms are arranged the N groups of guide channels, at most one generating mechanism is arranged on each group of guide channels, and a temperature sensing switch is connected on the guide channels, and a preset temperature threshold is input through the temperature sensing switch; A plurality of power generating mechanisms are respectively used for thermoelectric power generation, and N is apositive integer. The thermal power generation device has the advantages that the power supply voltage is stable and the power supply can be continuously supplied.