The utility model discloses a gas insulation switch cabinet air chamber pressure state on -line monitoring device, including a plurality of pressure sensor, serial server, switch, control host computer, condition assessment host computer. Pressure sensor installs among each air chamber, the interior pressure value of real -time recording air chamber, and the signal transmission that will be correlated with connects to serial server, and serial server is then through signal transmission to control host computer, the condition assessment host computer of net twine with pressure sensor to taken measures in advance by external control, reduce to minimum with the trouble. Monitor simultaneously host computer and condition assessment host computer to gas pressure value save, record and analysis gas pressure variation tendency and slewing rate, provide condition assessment analyzing image, set up alarm valve value according to the variation tendency, trigger the monitoring system action, the suggestion maintainer take measures.