The invention discloses an online monitoring system of a GIS (Gas Insulated Switchgear) switch cabinet, which comprises a cloud server, a monitoring host, a communication module, a voltage measuring circuit, a current measuring circuit and a switch measuring circuit; wherein the voltage measuring circuit is used for measuring voltage values of an energy storage motor and a coil of a circuit breaker in the switch cabinet and transmitting a measurement result to the monitoring host; the current measuring circuit is used for measuring current values of the energy storage motor and the coil of thecircuit breaker in the switch cabinet and transmitting a measurement result to the monitoring host; the switch measuring circuit is used for detecting the on-off between the energy storage motor andthe coil of the circuit breaker in the switch cabinet and a power supply and transmitting a detection result to the monitoring host. According to the online monitoring system of the invention, voltagedata, current data and on-off data of the energy storage motor and the coil in the switch cabinet are measured by utilization of measuring circuits, so as to monitor a working state of the circuit breaker in real time, thereby enabling power maintenance personnel to know the specific condition of the current switch cabinet in real time and timely discover potential safety hazards and fault reasons.