Electrochemical measurement electrode device for large scale facility service is developed.With start-up and shutdown process during verification test,304SS electrochemical corrosion potential(ECP)response is successfully on-line measured.The results indicated that ECP for 304SS first reduced,then plateaued and finally increased.In the plateaued stage,the ECP for 304SS is 0.26VSHE and the measured value is duplicated.The device design and preliminary on-line monitoring test provides some guidance on its practical engineering application.