The invention relates to a warning method and a self-energy taking warning indicator for overheating of electric system joints and belongs to the technical field of electric system running safety. The self-energy taking warning indicator for the overheating of electric system joints comprises a shell (10), an alternating current energy taking loop (1) arranged in the shell, a high-frequency absorbing loop (2), an alternating current amplitude limiting loop (3), a rectifying loop (4), a direct current voltage stabilizing loop (5), a heat energy releasing loop (6), a thermistor loop (7), a red lamp loop (8) and a green lamp loop (9). When the temperature of the contact surface of a joint is 20 to 30 degrees centigrade higher than a normal temperature due to the increase of contact resistance, the self-energy taking warning indicator emits red warning light which can be easily observed by a professional worker and discovered by people, the professional worker or people report to an electric power department so as to enable the circuit running maintainer to obtain the report early, the maintainer rushes to the scene in first time to use the simplest method to remove an oxide film, and then the maintainer fastens nuts; the hidden trouble which may cause power outage is eliminated at the initial budding stage.