The utility model provides a from looks enclosed bus state of insulation on -line monitoring system, this monitoring system contains: monitoring main website, network communication device, monitoring sub -station and sensor group, sensor group sets up inside the generating line shell for the air temperature and humidity in the monitoring generating line shell and the condition of discharging on insulator surface, the monitoring sub -station links to each other with sensor group for collect air temperature and humidity and the surperficial condition of discharging and the output of insulator in the generating line shell, the monitoring main website passes through network communication device and monitors the sub -station to link to each other for show air temperature and humidity and the condition of discharging on insulator surface in the analysis generating line shell, and with the condition of discharging on air temperature and humidity in the generating line shell and insulator surface with preset threshold comparison, alarm signal is sent when presetting the threshold value to the surperficial condition of discharging of air temperature and humidity when the generating line shell in and insulator.