The utility model discloses a transformer oil chromatography on -line monitoring system, including transformer and the on -line monitoring device of setting on moving platform, on -line monitoring device includes hydrocarbon separation unit, six -way valve, carrier gas unit, chromatographic column, gaseous detecting element, data acquisition the control unit and communication module, and the fueltap of getting of transformer communicates with hydrocarbon separation unit, and hydrocarbon separation unit's the end of giving vent to anger communicates to the on -line monitoring device 0 of six -way valve, and hydrocarbon separation unit's the end that produces oil passes through the vacuum circulating oil pump and communicates with the transformer oil return valve, six -way valve and carriergas unit and chromatographic column intercommunication, the chromatographic column passing through gases detecting element be connected with data acquisition the control unit, and data acquisition the control unit passes through communication module and backend server intercommunication, and communication module includes wireless communication port and wired communication port. The utility modeldiscloses can remove on -line monitoring device as required, can realize wired purpose that can realize real -time wireless monitoring transformer running state again, and guarantee the dry free fromadmixture of carrier gas.