The invention belongs to the technical field of maintenance devices of electric power equipment, especially relates to gas recovery, vacuum pumping and gas injection during disassembled major overhaulof SF6 gas insulation equipment, and specially relates to an online monitoring system of a SF6 recovery device. The online monitoring system of the SF6 recovery device comprises a pressure transducer, a differential amplification circuit, a processor unit, an Ethernet MAC and PHY interface circuit, a liquid crystal screen interface circuit, a field effect transistor output circuit, a virtual serial port circuit and a power supply unit, the pressure transducer is arranged on the SF6 gas recovery device and connected with the differential amplification circuit, the differential amplification circuit, the Ethernet MAC and PHY interface circuit, the liquid crystal screen interface circuit, the field effect transistor output circuit and the virtual serial port circuit are all connected with the processor unit, and the power supply unit supplies power to the processor unit, the Ethernet MAC and PHY interface circuit and the differential amplification circuit. According to the online monitoring system, the SF6 recovery device can be monitored in real time, great convenience is brought to the maintenance operation, and hidden risks are reduced.