The utility model discloses a capacitor bank on -line monitoring device, including sensor group and on -line monitoring unit, sensor group includes inlet wire terminal voltage current detection unit, leading -out terminal voltage current detection unit and temperature and humidity measurement unit, and inlet wire terminal voltage current detection unit, leading -out terminal voltage current detection unit all include electron voltage transformer and electronic current mutual -inductor, and the temperature and humidity measurement unit is including installing in on -line monitoring 1 node and the inside on -line monitoring 2 of condenser. The utility model discloses can carry out real -time on -line monitoring to power capacitor bank equipment, can remote monitoring with control the action of capacitor bank running state and capacitor bank, and can detect based on current temperature and accurately predict the temperature value in future, for dispel the heat to capacitor bank, functions such as early warning and warning provide the information basis.