The utility model discloses an identified signal generating device of the excitation system of a synchronous generator, which comprises a power source unit (7), a signal generating unit (8) and a controlling unit (9); the power source unit supplies the required working power for the other two units; the signal generating unit is respectively connected with the three-phase voltage and the neutral point at an electric generator terminal, and the identified signals required by the model identification test of the excitation system are superposed to the voltage signals at the electric generator terminal according to the control signals provided by the controlling unit, and then the four integrated signals superposed with the identified signals are accessed into the input port of the excitation system; the controlling unit is used for generating pseudo-random signals or step signals to provide the signals to the signal generating unit or to be directly output from the signal output port. The device provides a new testing device for the electrical power system, therefore, only solves the problem that model identification test of the excitation system is performed to the electric generator without a reserved additional signal input port is solved, but also the testing equipment is simplified, and the testing efficiency can be improved.