The utility model belongs to the technical field of engine test equipment, and particularly relates to a novel electric heater fault on-line monitoring device. The device comprises an S7-200 programmable logic controller, an intelligent voltage detection module, an alternating current fuse, an intelligent current detection module, a communication cable, an air switch QF1 and an air switch QF2. AnRS485 communication interface 1 of the S7-200 programmable logic controller is respectively connected with RS485 communication interfaces of the intelligent current detection module and the intelligent voltage detection module through communication cables; the intelligent current detection module is used for detecting current flowing through the electric heater, and the intelligent voltage detection module is used for detecting voltage on the electric heater; according to the utility model, whether the heating pipe breaks down or not is monitored on line, and when the heating pipe breaks down,a fault alarm can be given to prompt an operator that the heating pipe breaks down and needs to be maintained; power-off monitoring is not needed, monitoring can be conducted while working is conducted, and the control precision of original equipment is not affected.