The invention discloses a method, system and device for monitoring the temperature of a power capacitor based on an RFID and belongs to the technical field of power transmission and transformation. The method comprises a step of determining temperature measurement points of power capacitors to be measured, arranging high-precision temperature sensing tags at the temperature measurement point, andassembling power capacitors, a step of matching the plurality of assembled power capacitors with a plurality of dipole antennas such that a reader-writer is in network connection with the high-precision temperature sensing tags through the antennas, and a step of obtaining temperature data of the temperature measurement points of the power capacitors to be measured through the high-precision temperature sensing tags, preprocessing the temperature data through the reader-writer, transmitting the data to a centralized monitoring center, and monitoring the temperature of the power capacitors. According to the invention, the temperature precision of the power capacitors for a power system transformer substation can be greatly improved, meanwhile, the operation temperature of the power capacitors can be monitored in real time through the ubiquitous Internet of Things technology, a corresponding early warning value is set through monitoring software, and the intelligent perception of the operation states of the power capacitors is achieved.