The invention relates to an automatic temperature measuring and early warning device and method for a substation capacitor, and mainly solves problems in the prior art that heat generation overhaulingperformed on a capacitor by adopting an infrared imaging instrument cannot test the temperature in a closed environment, the test result is affected by the season, the time and the surface smoothnessof test equipment, and that the infrared test equipment is expensive and cannot perform continuous monitoring on the temperature of high-voltage electrical equipment for a long time. The automatic temperature measuring and early warning device and method provided by the invention for the substation capacitor ensure real-time and accurate monitoring for the temperature of the substation capacitor.