The invention discloses a real-time online monitoring method of power cable insulation. The method includes: installing a residual current detecting device and a temperature detecting device at a cable outlet, laying a communication cable, and setting a background monitoring system. Operation status of the power cable is monitored in real time in a non-contact manner, so that abnormal conditions of the power cable can be detected effectively and timely, fast processing is achieved, reliability of safe operation of the power cable is improved practically, and influence of power failure to the operation and damage of voltage increasing impact to the power cable are reduced. Service life of the power cable is prolonged effectively. Influence to power supply due to overloading, virtual access and the like is prevented. Detecting intensity of management staff is relieved evidently, detecting precision is improved, an equipment operation database is generated according to needs to provide detailed data for equipment maintenance and equipment update, and management effect and management level are improved evidently.